Immunity to hepatitis A and B persists for at least 15 years after immunisation of adolescents with a combined hepatitis A and B vaccine

BackgroundThe exact duration of antibody persistence to hepatitis A and B and the need for booster dosing following primary immunisation remains undefined. A long-term study was designed to follow antibody persistence and immune memory on an annual basis for up to 15 years following vaccination during adolescence.MethodsSubjects received a combined hepatitis A and B vaccine (Twinrix™, GSK Vaccines, Belgium) at 12–15 years of age, either as 2-dose of the adult formulation or 3-dose of the paediatric formulation. Blood samples were taken every year thereafter to assess antibody persistence and immune memory to hepatitis A and B. Antibodies to hepatitis A virus (anti-HAV) and hepatitis B surface antigen (anti-HBs) were measured at Years 11–15. At Year 15 immune memory was further assessed by measuring the anamnestic response to a challenge dose of the monovalent vaccine, which was administered to subjects whose antibody concentrations fell below the pre-defined cut-offs (anti-HAV: <15 mIU/mL; anti-HBs: <10 mIU/mL).Results209 subjects returned for follow-up at Year 15 of whom 162 were included in the long-term according-to-protocol immunogenicity cohort. All subjects remained seropositive for anti-HAV antibodies, while 81.1% and 81.8% still had anti-HBs antibodies ≥10 mIU/mL in the 2- and 3-dose groups, respectively. Following hepatitis B vaccine challenge dose administration to 19 subjects, all except one in the 3-dose group, mounted a robust anamnestic response. The safety and reactogenicity profile of the hepatitis B challenge was consistent with previous experience.ConclusionImmunity to hepatitis A and B persists 15 years after adolescent vaccination with a combined hepatitis A and B vaccine. Highly effective anamnestic response indicates that a booster dose should not be required for 15 years after primary vaccination.Trial registrationhttp://www.clinicaltrials.gov NCT00875485.     

Persistence of hSBA titers elicited by the meningococcal serogroup B vaccine menB-FHbp for up to 4 years after a 2- or 3-dose primary series and immunogenicity,safety, and tolerability of a booster dose through 26 months

BackgroundTo demonstrate extended protection against meningococcal serogroup B (MenB) disease after MenB-FHbp (bivalent rLP2086) vaccination, this study evaluated immunopersistence through 26 months following MenB-FHbp boosting after 2 or 3 primary doses in adolescents.Study designThis phase 3, open-label study was an extension of 3 phase 2 studies with participants aged 11–18 years randomized to receive primary MenB-FHbp vaccination following 1 of 5 dosing schedules or control. A booster dose was administered 48 months after the primary series. Immunopersistence through 48 months after the last primary dose (persistence stage) and 26 months postbooster (booster stage) was determined by serum bactericidal assays using human complement (hSBAs) against 4 vaccine-heterologous test strains. Safety evaluations included adverse events (AEs) and local and systemic reactions.ResultsOverall, 698 and 304 subjects enrolled in the persistence and booster stages, respectively. hSBA titers declined in all groups during 12 months postprimary vaccination, then remained stable through 48 months. One month postbooster, 93.4–100.0% of subjects achieved hSBA titers ≥ lower limit of quantitation against each test strain; percentages at 12 and 26 months postbooster were higher than at similar time points following primary vaccination. Primary and booster MenB-FHbp vaccinations were well tolerated, with ≤ 12.5% of subjects reporting AEs during each stage. The most common local (reported by 84.4–93.8% of subjects) and systemic (68.8–76.6%) reactions to the booster were injection site pain and fatigue and headache, respectively; ≤ 3.7% of subjects reported severe systemic events.ConclusionProtective hSBA titers initially declined but were retained by many subjects for 4 years irrespective of primary MenB-FHbp vaccination schedule. Boosting at 48 months after primary vaccination was safe, well tolerated, and induced immune responses indicative of immunological memory that persisted through 26 months. Booster vaccination during late adolescence may prolong protection against MenB disease.     

Long-term follow-up of Japanese encephalitis chimeric virus vaccine: Immune responses in children

BackgroundA single dose of live attenuated Japanese encephalitis chimeric virus vaccine (JE-CV) was shown to be immunogenic and well tolerated when given either as a booster to formalin-inactivated Japanese encephalitis (JE)-vaccine (mouse brain-derived vaccine [MBDV])-primed 2–5-year-olds, or as a primary vaccination to JE-vaccine-naïve 12–24-month-old toddlers in Thailand. A 5-year follow-up assessment of immune response persistence over time was conducted.MethodsFour additional visits (at 2, 3, 4, and 5 years) for immunologic assessments were added to the original 12-month open-label crossover study, in which 100 healthy children aged 2–5 years with a history of two-dose primary vaccination with MBDV (according to the Thai Expanded Program for Immunization schedule), and 200 healthy JE-vaccine-naïve 12–24-month-old toddlers, were randomized 1:1 to receive JE-CV, containing ⩾4 log₁₀ plaque forming units, 1 month before or after hepatitis A control vaccine.ResultsIn MBDV-primed 2–5-year-olds (n = 78), the immune response to the JE-CV vaccine persisted up to at least 5 years after vaccination with a single dose of JE-CV, with all (n = 78) children seroprotected at the year 5 visit (geometric mean titers [GMT]: 252 1/dil). There was no decrease of seroprotection rate over time (100% at 6 months post-vaccination and 96.8% (90.3–98.9) at 5 years post-vaccination). In JE-vaccine-naïve toddlers, a protective immune response persisted up to at least 5 years in 58.8% (50.9–66.4) after a single-dose administration of JE-CV (GMT 26.7 1/dil; sensitivity analysis).ConclusionsA single-dose of JE-CV as a booster following MBDV administration provided long-lasting immunity. In JE-vaccine-naïve toddlers, despite relatively high seroprotection rates persisting over time, a subsequent booster dose is recommended following a JE-CV primary vaccination for long-term protection.This study was registered on www.clinicaltrials.gov (NCT00621764).     

Persistence of antibodies and immune memory to hepatitis B vaccine 20 years after infant vaccination in Thailand

Booster vaccination against hepatitis B (HBV) is not currently recommended, although debate continues on the duration of protection after priming. We assessed antibody persistence and immune memory to hepatitis B 20 years after priming with a recombinant HBV-vaccine during infancy. Infants were vaccinated at birth, 1, 2 and 12 months of age. A subset received a booster dose at Year 5. Antibody persistence was measured approximately yearly until Year 20. Immune memory was assessed by administration of HBV booster dose. At Year 20, anti-HBs seroprotection rates and GMCs tended to be higher in Year 5 boosted than unboosted recipients (83.9% versus 60.5%). After the Year 20 booster dose, anti-HBs anamnestic responses were within the same range 95.8% of subjects in both groups. Primary and booster vaccination with HBV-vaccine in infants induces sustained seroprotection and immune memory against hepatitis B for up to 20 years. Higher persisting seroprotection rates in subjects boosted at Year 5 did not translate into apparent differences in immune memory in a high endemic country.     

Impact of HIV status and vaccination schedule on bacterial nasopharyngeal carriage following infant immunisation with the pneumococcal non-typeable Haemophilus influenzae protein D conjugate vaccine in South Africa

BackgroundNasopharyngeal carriage (NPC) of Streptococcus pneumoniae is a precondition for pneumococcal disease and a source of transmission. This trial evaluated NPC of S. pneumoniae and other pathogens post-vaccination with the pneumococcal non-typeable Haemophilus influenzae (NTHi) protein D conjugate vaccine (PHiD-CV) in human immunodeficiency virus (HIV)-infected (HIV+), HIV-exposed-uninfected (HEU), and HIV-unexposed-uninfected (HUU) South African children.MethodsIn this phase III, open, single‐centre, controlled study (ClinicalTrials.gov: NCT00829010), 484 children were stratified by HIV status: 83 HIV+, 101 HEU, and 300 HUU. HIV+ and HEU children received a 3 + 1 PHiD-CV vaccination schedule: primary vaccination, age 6/10/14 weeks, and booster dose, age 9–10 months. HUU infants were randomised (1:1:1) to 3-dose priming and booster (HUU/3+1); 3-dose priming without booster (HUU/3+0); or 2-dose priming and booster (HUU/2+1). Bacterial NPC was assessed 8 times up to 24–27 months of age.ResultsOverall pneumococcal carriage rates were similar across 3+1 groups irrespective of HIV status; trends towards higher carriage rates in the HIV+ than HEU and HUU/3+1 groups were observed at 24–27 months of age. In HUU children, carriage of any pneumococcal serotype was similar for the three different dosing schedules at all timepoints; carriage of vaccine-type pneumococci tended to be lower at 16–19 months and 24–27 months of age in children who had received a booster dose (HUU/2+1 and HUU/3+1 groups) than in the HUU/3+0 group. Carriage rates of NTHi, Staphylococcus aureus and Moraxella catarrhalis were comparable between all groups.ConclusionsHIV infection or exposure did not seem to alter the effect of PHiD-CV on pneumococcal NPC in children during their first 2 years of life. NPC prevalence of vaccine-type pneumococci following vaccination series tended to be lower in children who had received a booster dose in comparison to those who had not.     

Hepatitis A antibody persistence 8 and 10 years after 1-dose and 2-dose vaccination in children from Panama

BackgroundHepatitis A virus (HAV) remains a global public health concern, which is potentially growing in Latin America, due to an expected shift from high to intermediate endemicity levels. The use of HAV vaccines in pediatric national immunization programs (NIPs), either as a 2-dose or a 1-dose schedule, has been explored in Latin American countries; however, evidence demonstrating long-term protection in this population is limited in the region. We evaluated long-term antibody persistence following a 1-dose partial series and the recommended 2-dose schedule used in Panama’s pediatric NIP.MethodsTwo independent cross-sectional serological surveys were conducted at year 8 (Y8) and Y10 following vaccination under the NIP with 1 or 2 doses of an inactivated HAV vaccine (Havrix, GSK). Seropositivity (anti-HAV antibody concentration ≥ 15 mIU/mL) rates and antibody geometric mean concentrations (GMCs) were assessed at each serosurvey. Non-inferiority of 1 dose versus 2 doses was also explored.ResultsThis study (NCT02712359) included 600 and 599 children at Y8 and Y10 post-vaccination, respectively. Seropositivity rates were 74.3% (95% confidence interval [CI]: 69.0; 79.2) and 97.7% (95% CI: 95.3; 99.1) at Y8 and 71.9% (95% CI: 66.4; 76.9) and 96.3% (95% CI: 93.5; 98.2) at Y10, in the 1-dose and 2-dose groups, respectively. Antibody GMCs were lower in the 1-dose versus the 2-dose group in both surveys. Non-inferiority was not demonstrated since the lower limit of the 2-sided 95% CI for the between-group difference in seropositivity rates (1-dose minus 2-dose) was < ?10%.ConclusionAnti-HAV antibody persistence was observed in lower percentages of children receiving 1 dose versus 2 doses of Havrix, at 8 and 10 years post-vaccination in Panama. Further investigations are needed to confirm antibody persistence and conclude on the protection afforded beyond 10 years in the pediatric population in Latin America.     

Relative effectiveness of booster vs. 2-dose mRNA Covid-19 vaccination in the Veterans Health Administration: Self-controlled risk interval analysis

ObjectiveTo estimate relative effectiveness of the booster mRNA Covid-19 vaccination versus the 2-dose primary series for both Delta and Omicron variants with self-controlled study design.MethodsWe used the Veterans Health Administration (VHA) Corporate Data Warehouse to identify U.S. Veterans who received the 2-dose primary mRNA Covid-19 vaccine series and a mRNA Covid-19 booster, and who had a positive SARS-CoV-2 test during the Delta (9/23/2021–11/30/2021) or Omicron (1/1/22–3/19/22) predominant period. Among them, we conducted a self-controlled risk interval (SCRI) analysis to compare odds of SARS-CoV-2 infection during a booster exposure interval versus a control interval. Exposures were a control interval (days 4–6 post-booster vaccination, presumably prior to gain of booster immunity), and booster exposure interval (days 14–16 post-booster vaccination, presumably following gain of booster immunity). Cases had a positive PCR or antigen SARS-CoV-2 test. Separately for Delta and Omicron periods, we used conditional logistic regression to calculate odds ratios (OR) of a positive test for the booster versus control interval and calculated relative effectiveness of booster versus 2-dose primary series as (1-OR)*100. The SCRI approach implicitly controlled for time-fixed confounders.ResultsWe found 42 individuals with a positive SARS-CoV-2 test in the control interval and 14 in the booster exposure interval during the Delta period, and 141 and 70, respectively, in the Omicron period. For the booster versus 2-dose primary series, the odds of infection were 70% (95 %CI: 42%, 84%) lower during the Delta period and 54% (95 %CI: 38%, 66%) lower during Omicron. In sensitivity analyses among those with prior Covid-19 history, and age stratification, ORs were similar to the main analysis.ConclusionsBooster vaccination was more effective relative to a 2-dose primary series during the Delta and Omicron predominant periods, and the relative effectiveness was consistent across age groups.     

Human papillomavirus vaccination coverage using two-dose or three-dose schedule criteria

In October 2016, the Advisory Committee on Immunization Practices (ACIP) updated the human papillomavirus (HPV) vaccination recommendation to include a 2-dose schedule for U.S. adolescents initiating the vaccine series before their 15th birthday. We analyzed records for >4 million persons aged 9–17 years receiving any HPV vaccine by the end of each quarter during January 1, 2014–September 30, 2016 from six Immunization Information Systems Sentinel Sites, and reclassified HPV vaccination up-to-date coverage according to the updated recommendations. Compared with HPV vaccination up-to-date coverage by the 3-dose schedule only, including criteria for either a 2-dose or 3-dose schedule increased up-to-date coverage in 11–12, 13–14, and 15–17 year-olds by 4.5–8.5 percentage points. The difference between 3-dose up-to-date coverage and 2- or 3-dose up-to-date coverage was greatest in late 2016. These data provide baseline HPV vaccination coverage using current ACIP recommendations.     

Primary and booster vaccination with an inactivated poliovirus vaccine (IPV) is immunogenic and well-tolerated in infants and toddlers in China

IntroductionReplacing live-attenuated oral poliovirus vaccines (OPV) with inactivated poliovirus vaccines (IPV) is part of the global strategy to eradicate poliomyelitis. China was declared polio-free in 2000 but continues to record cases of vaccine-associated-poliomyelitis and vaccine-derived-poliovirus outbreaks. Two pilot safety studies and two larger immunogenicity trials evaluated the non-inferiority of IPV (Poliorix™, GSK Vaccines, Belgium) versus OPV in infants and booster vaccination in toddlers primed with either IPV or OPV in China.MethodsIn pilot safety studies, 25 infants received 3-dose IPV primary vaccination (Study A, www.clinicaltrial.gov NCT00937404) and 25 received an IPV booster after priming with three OPV doses (Study B, NCT01021293). In the randomised, controlled immunogenicity and safety trial (Study C, NCT00920439), infants received 3-dose primary vaccination with IPV (N = 541) or OPV (N = 535) at 2,3,4 months of age, and a booster IPV dose at 18-24 months (N = 470, Study D, NCT01323647: extension of study C). Blood samples were collected before and one month post-dose-3 and booster. Reactogenicity was assessed using diary cards. Serious adverse events (SAEs) were captured throughout each study.ResultsStudy A and B showed that IPV priming and IPV boosting (after OPV) was safe. Study C: One month post-dose-3, all IPV and ≥98.3% OPV recipients had seroprotective antibody titres towards each poliovirus type. The immune response elicited by IPV was non-inferior to Chinese OPV. Seroprotective antibody titres persisted in ≥94.7% IPV and ≥96.1% OPV recipients at 18–24 months (Study D). IPV had a clinically acceptable safety profile in all studies. Grade 3 local and systemic reactions were uncommon. No SAEs were related to IPV administration.ConclusionTrivalent IPV is non-inferior to OPV in terms of seroprotection (in the Chinese vaccination schedule) in infant and toddlers, with a clinically acceptable safety profile.     

Single Ad26.COV2.S booster dose following two doses of BBIBP-CorV vaccine against SARS-CoV-2 infection in adults: Day 28 results of a phase 1/2 open-label trial

BackgroundThe inactivated COVID-19 whole-virus vaccine BBIBP-CorV has been extensively used worldwide. Heterologous boosting after primary vaccination can induce higher immune responses against SARS-CoV-2 than homologous boosting. The safety and immunogenicity after 28 days of a single Ad26.COV2.S booster dose given at different intervals after 2 doses of BBIBP-CorV are presented.MethodsThis open-label phase 1/2 trial was conducted in healthy adults in Thailand who had completed 2-dose primary vaccination with BBIBP-CorV. Participants received a single booster dose of Ad26.COV2.S (5 × 10¹⁰ virus particles) 90–240 days (Group A1; n = 360) or 45–75 days (Group A2; n = 66) after the second BBIBP-CorV dose. Safety and immunogenicity were assessed over 28 days. Binding IgG antibodies to the full-length pre-fusion Spike and anti-nucleocapsid proteins of SARS-CoV-2 were measured by enzyme-linked immunosorbent assay. The SARS-CoV-2 pseudovirus neutralization assay and live virus microneutralization assay were used to quantify the neutralizing activity of antibodies against ancestral SARS-CoV-2 (Wuhan-Hu-1) and the delta (B.1.617.2) and omicron (B.1.1.529/BA.1 and BA.2) variants. The cell-mediated immune response was measured using a quantitative interferon (IFN)-γ release assay in whole blood.ResultsSolicited local and systemic adverse events (AEs) on days 0–7 were mostly mild, as were unsolicited vaccine-related AEs during days 0–28, with no serious AEs. On day 28, anti-Spike binding antibodies increased from baseline by 487- and 146-fold in Groups A1 and A2, and neutralizing antibodies against ancestral SARS-CoV-2 by 55- and 37-fold, respectively. Humoral responses were strongest against ancestral SARS-CoV-2, followed by the delta, then the omicron BA.2 and BA.1 variants. T-cell–produced interferon-γ increased approximately 10-fold in both groups.ConclusionsA single heterologous Ad26.COV2.S booster dose after two BBIBP-CorV doses was well tolerated and induced robust humoral and cell-mediated immune responses measured at day 28 in both interval groups.Clinical Trials Registration. NCT05109559.     

Immunogenicity and safety of the third booster dose of the inactivated Japanese encephalitis vaccine in Korean children: A prospective multicenter study

The immunization schedule for the inactivated Japanese encephalitis (JE) vaccine in Korea is a two-dose primary series at 12–24 months of age and three booster doses at 12 months after primary schedule and at 6 and 12 years of age. The aim of this study was to investigate immunogenicity and safety of the third booster dose of the inactivated JE vaccine, as well as the long-term immunogenicity of the second booster dose in Korean children. Healthy children aged 11–13 years, primed and given four doses of inactivated JE vaccines were included. All subjects received the third booster dose of the JE vaccine. Neutralizing antibody (NTAb) titers were assessed before and 4–6 weeks after vaccination using plaque reduction neutralization test (PRNT), and were considered to be protective at ≥ 1:10. Local and systemic adverse events were monitored for 4 weeks after vaccination. Before and after booster vaccination, all seroprotection rates were 100%. Geometric mean titer (GMT) showed a 6.05–fold increase, from 139.11 (95% CI: 110.76, 174.71) to 841.53 (95% CI, 714.25, 991.50). The local tolerability and systemic safety profiles were favorable, with no serious adverse events. In conclusion, the third booster dose of the inactivated JE vaccine was demonstrated to be safe and immunogenic in Korean children when administered according to the current immunization schedule.     

Sustained antibody persistence for at least 15 years after a booster vaccination against tick-borne encephalitis following different primary vaccination schedules: Third 5-year follow-up

BackgroundVaccination is the best mode of protection against tick-borne encephalitis (TBE) and its sequelae. The duration of protection and the optimal interval of repeat booster doses are still debated. The current study evaluated the persistence of the antibody response 11–15 years after a first booster vaccination following different primary vaccination schedules with a TBE vaccine (Encepur Adults, manufactured by Bavarian Nordic, previously by GSK).MethodsThis phase IV, open-label, mono-centric extension study enrolled adults who had received (at ≥ 12 years of age) primary vaccination with one of three randomly assigned TBE vaccine schedules (rapid [group R], conventional [group C], or accelerated conventional schedule [group A]) followed by a booster dose 3 years later. The antibody response was measured annually from 11 to 15 years post-booster using a TBE virus neutralization test (NT). An NT titer of ≥ 10 was considered as a clinically meaningful threshold and surrogate for protection.ResultsIn total, 194 participants were enrolled and included in the per-protocol set; 188 completed the study. The percentage of participants with an NT titer ≥ 10 was 100% in group R and 99.0% in group A at all visits and ranged from 100% (year 11) to 95.8% (year 15) in group C. NT geometric mean titers were similar in the three study groups (181–267 in group R, 142–227 in group C, 141–209 in group A). NT geometric mean titers also remained high among participants ≥ 50 years old (98–206) and ≥ 60 years old (91–191) across study groups and time points.ConclusionsThis study showed neutralizing antibody persistence for at least 15 years after a first booster dose of the Encepur Adults TBE vaccine in all age groups evaluated, regardless of which primary vaccination schedule was given to adolescents or adults.Trial registry: ClinicalTrials.gov: NCT03294135.     

A phase 3, randomized,controlled, open-label study to evaluate the persistence up to 5 years of 1 or 2 doses of meningococcal conjugate vaccine MenACWY-TT given with or without 13-valent pneumococcal conjugate vaccine in 12–14-month-old children

BackgroundImmunogenicity and safety up to 5 years after administration of 1 or 2 doses of quadrivalent meningococcal serogroup A, C, W, and Y tetanus toxoid conjugate vaccine (MenACWY-TT) given alone or with 13-valent pneumococcal conjugate vaccine (PCV13) in children was investigated.MethodsThis phase 3 study randomized healthy 12–24-month-olds to MenACWY-TT at Month 0 (ACWY1d), MenACWY-TT at Months 0 and 2 (ACWY2d), MenACWY-TT and PCV13 at Month 0 (Co-Ad), or PCV13 at Month 0 and MenACWY-TT at Month 2 (PCV13/ACWY). Immune responses 1, 3, and 5 years after primary vaccination were evaluated with serum bactericidal activity using rabbit complement (rSBA) titers ≥ 1:8 and geometric mean titers (GMTs). Evaluation of serious adverse events up to 5 years after primary vaccination are reported.ResultsOf the 802 children randomized in the study, 619 completed the study through Year 5. Immune responses after vaccination declined over time but were higher 5 years after vaccination compared with levels before vaccination. At Year 5, the percentages of children with rSBA titers ≥ 1:8 across all serogroups were 20.5 %?58.6 %, 28.4 %?65.8 %, 23.9 %?52.8 %, and 19.4 %?55.8 % in the ACWY1d, ACWY2d, Co-Ad, and PCV13/ACWY groups, respectively. Comparable antibody persistence at Year 5 was observed for participants receiving 1 or 2 doses of MenACWY-TT, although GMTs were elevated in those who received 2 versus 1 dose. The percentage of children with protective antibody titers at Year 5 was similar in participants who received PCV13 and MenACWY-TT compared with that observed for participants who only received 1 or 2 MenACWY-TT doses. No new safety concerns were identified during the study period.ConclusionAntibody responses persisted in the majority of children up to 5 years after primary vaccination with MenACWY-TT administered in a 1- or 2-dose regimen with or without PCV13, with no new safety concerns identified.ClinicalTrials.gov Identifier NCT01939158; EudraCT number 2013–001083-28.     

Long-term antibody persistence after a booster dose of quadrivalent meningococcal ACWY-tetanus toxoid conjugate vaccine in healthy 5-year-old children

BackgroundTo provide continuing protection, available meningococcal vaccines must provide long-term persistence of circulating functional antibodies against prevalent serogroups causing invasive meningococcal disease (IMD). This study assessed antibody persistence and safety of the quadrivalent meningococcal vaccine conjugated to tetanus toxoid (MenACWY-TT) and the meningococcal serogroup C vaccine conjugated to Corynebacterium diphtheriae CRM₁₉₇ protein (MenC-CRM) for up to 6 years after booster dosing in children.MethodsIn the primary vaccination study, children were vaccinated at age 12 to 23 months. In the first extension study, children who completed the primary study received a booster dose 4 years later with the same primary vaccine. The current study assessed antibody persistence at 2 to 6 years postbooster against each of the 4 meningococcal serogroups using serum bactericidal assays using rabbit (rSBA) or human (hSBA) complement with antibody titer thresholds of ≥1:8 or ≥1:4, respectively, and geometric mean titers (GMTs). Safety evaluations during this period included serious adverse events (SAEs) related to vaccination and any event related to lack of vaccine efficacy.ResultsA total of 184 subjects were enrolled (MenACWY-TT = 159; MenC-CRM = 25). For MenACWY-TT, the percentages of subjects with rSBA titers ≥1:8 ranged from 96.7% to 100% across serogroups at 2 years postbooster and 71.6% to 94.0% at 6 years postbooster; rSBA GMTs decreased from Year 2 to 4 and generally remained stable thereafter. The percentages of subjects in the MenACWY-TT group with hSBA titers ≥1:4 were 70.0% to 100% across serogroups at 2 years postbooster and 58.5% to 98.5% at 6 years postbooster. No lack of efficacy, SAEs, or vaccine-related adverse events were reported.ConclusionsThe persistence of rSBA and hSBA antibodies was shown up to 6 years postbooster (10 years postprimary vaccination) with either MenACWY-TT or MenC-CRM, suggesting that this schedule may provide long-term protection against IMD. Clinicaltrials.gov: NCT01900899.     

Safety and immune response after two-dose meningococcal C conjugate immunization in HIV-infected children and adolescents in Rio de Janeiro,Brazil

We aimed to evaluate immunogenicity and adverse events (AEs) after a booster dose of Meningococcal C conjugated (MCC) vaccine in HIV-infected children and adolescents, who had a previous low seroconversion rate after priming with MCC, at a reference HIV-care center in Rio de Janeiro.Methods2–18 years old HIV-infected subjects with CD4+ T-lymphocyte cell (CD4) ≥15%, without active infection or antibiotic use, were enrolled to receive 2 doses of conjugated meningococcal C oligosaccharide-CRM197 12–18 months apart. All patients were evaluated before and 1–2 months after immunization for seroprotection [defined as human serum bactericidal activity (hSBA) titer ≥1:4]. AEs were assessed at 20 min, 3 and 7 days after each dose. Factors independently associated with seroprotection were studied.Results156 subjects were enrolled and 137 received a booster MCC dose. 55% were female, and median age was 12 years. Eight-nine percent were receiving combined antiretroviral therapy (cART) at the booster visit (median duration of 7.7 years), 59.9% had undetectable viral load (VL) at baseline, and 56.2% at the booster visit. Seroprotection was achieved in 78.8% (108/137) subjects, with a significantly higher GMT than after the priming dose (p < 0.01). Mild AEs were experienced after a second MCC dose (38%). In logistic regression, undetectable viral load at entry [odds ratio (OR) = 7.1, 95% confidence interval (95%CI): 2.14–23.37], and probably higher CD4 percent at the booster immunization visit (OR): 1.1, 95%CI: 1.01–1.17 were associated with seroprotection after a booster dose of MCC.ConclusionA booster dose of MCC was safe and induced high seroprotection rate even 12–18 months after priming. MCC should be administered after maximum virologic suppression has been achieved. These results support the recommendation of 2-dose of MCC for primary immunization in HIV-infected children and adolescents with restored immune function.     

Immunogenicity and persistence from different 3-dose schedules of live and inactivated polio vaccines in Chinese infants

BackgroundOPV is the only poliovirus vaccine used in the China EPI system, although IPV is available in the private market. We compared immunigencity and persistence among different schedules of IPV and OPV.Methods536 Chinese infants were enrolled into 4 groups receiving different schedules administered at 2, 3, and 4 months of age: IPV–OPV–OPV, IPV–IPV–OPV, IPV–IPV–IPV, and OPV–OPV–OPV. The I–I–I group received an 18-month IPV booster dose. Blood samples were collected before the first dose, after the third dose, and at 18 months for all groups, and also after the booster dose for the I–I–I group. Polio neutralizing antibody titers were assessed, and seroprotection rates were calculated after primary immunization and at 18 months of age.ResultsBefore the first dose, GMTs of the 4 groups ranged from 2.96 to 6.89, and seroprotection rates ranged from 17.6% to 54.3%. After 3 doses, the GMT of the I–O–O and I–I–O groups ranged from 901.09 to 1,110.12, and the GMT of the I–I–I group range was 212.02 to 537.52, significantly lower than for the 2 sequential schedules (P < 0.001). Seroprotection rates were 98.1% to 100%, with no significant differences among groups. At 18 months of age, the GMTs declined to a range of 527.00 to 683.44 in the I–O–O and I–I–O groups, and declined to 150.04 to 239.89 in the I–I–I group, significantly lower than for the other 3 groups (P < 0.001).ConclusionsThe sequential schedules achieved high GMTs and seroprotection. The IPV-only schedule achieved high seroprotection but with lower GMTs. Sequential schedules are suitable for China. With the 2 sequential schedules, GMTs remained high at 18 months of age and were not inferior to the OPV-only schedule. Thus, with a sequential schedule, the booster dose could be given at 4 years of age, the same age as the current OPV booster dose.     

The predicted persistence and kinetics of antibody decline 9 years after pre-school booster vaccination in UK children

BackgroundLong term follow-up of vaccine trials is essential to establish the duration of protection. In the context of worldwide concern about rising pertussis incidence, estimates of antibody persistence after vaccination, which do not account for the rise in antibody due to natural boosting or infection, may overestimate the degree of protection afforded by pertussis vaccines.MethodsThis was a 5 year follow up study of a randomised controlled trial of diphtheria, tetanus, pertussis and polio booster vaccines in UK children aged 3.5–5 years. Antibody persistence was measured at 1 month, 1, 3, and 5 years after vaccination and the kinetics of antibody decline were modelled longitudinally. Estimates of predicted antibody persistence 9 years after the pre-school booster were derived from model parameters.ResultsAntibody levels 9 years after vaccination were predicted to be above accepted thresholds for protection for diphtheria, tetanus and polio. Antibody responses to pertussis toxoid were undetectable in 49% of children at the 5 year follow up visit, and responses were predicted to be undetectable in 69% (95% CI 45–88%) of children by the time of their teenage booster at 13–14 years of age.ConclusionsThere is no defined correlate of protection for pertussis. However, the large proportion of participants in this study with undetectable pertussis antibody levels at both measured and predicted timepoints suggests sub-optimal immunity in adolescence. Adding pertussis to the teenage booster for UK children as is done in other countries, would enhance immunity in adolescence.     

Persistence of protective anti-poliovirus antibody levels in 4-year-old children previously primed with Picovax®, a trivalent,aluminium-adjuvanted reduced dose inactivated polio vaccine

BackgroundTo meet the demand for effective and affordable inactivated polio vaccines (IPVs), a reduced dose, aluminium hydroxide (Al(OH)₃)-adjuvanted IPV vaccine was developed (IPV-Al, Picovax®) and evaluated in clinical trials. The present trial is an extension of two previous trials (a primary and a booster trial). The aim was to evaluate the persistence of seroprotective antibodies (poliovirus type-specific antibody titre ≥ 8) in 4-year-old children who previously received IPV–Al as primary and booster vaccine doses and to determine the potential booster response and safety profile of an additional dose of IPV-Al.MethodsChildren participating in the two previous trials were invited to receive one additional dose of IPV-Al at 4 years of age (2.5 years after the booster dose) and to have their blood samples collected to measure the pre- and post-vaccination antibody titres. Systemic adverse events (AEs) and local reactogenicity were recorded.ResultsAt study entry, the seroprotection rates were 89.2%, 100% and 91.1% against poliovirus type 1, 2 and 3, respectively. The additional vaccination with IPV-Al boosted the level of poliovirus type 1, 2 and 3 antibodies to above the seroprotection threshold for all but one subject, i.e., 99.4% for type 1 and 100% for types 2 and 3. The additional dose induced a robust booster response of a 26.3-, 13.9- and 30.9-fold increase in titre for poliovirus types 1, 2 and 3, respectively. The vaccine was well tolerated, with only mild and transient AEs reported.ConclusionsThe present trial demonstrated that the primary vaccination with an aluminium-adjuvanted reduced dose IPV induced a persistent immune memory as evidenced by the robust anamnestic response when the subjects were re-exposed to the antigen 2.5 years after the last dose. Thus, the IPV-Al is an efficient and safe addition to increase the availability of inactivated polio vaccines globally. (ClinicalTrials.gov reg no. NCT04448132).     

A randomized open-label trial of 2-dose or 3-dose pre-exposure rabies prophylaxis among Thai children

BackgroundWorld Health Organization changed the recommendation for pre-exposure rabies prophylaxis from 3-dose to 2-dose regimen in 2018. Given limited data of 2-dose regimens in pediatric population, this study aimed to compare the immunogenicity between 2-dose and 3-dose pre-exposure rabies immunization.MethodsThis study was conducted among healthy children aged 2–12 years. They were randomized to 2-dose vaccination (2D) on days 0 and 28 or 3-dose vaccination (3D) on days 0, 7, and 28. Purified Vero cell rabies vaccine (PVRV-Verorab™) was administered intramuscularly. Rabies virus neutralizing antibody (RVNA) titers were measured at 3 time points: 14-day after complete vaccination, 1-year pre-booster vaccination, and 7-day post-booster dose to mimic scenario of rabies exposure. RVNA titers ≥0.5 IU/ml were considered adequate antibody. T cell specific response to rabies vaccine antigen was measured using the interferon-gamma enzyme linked immunospot assay.ResultsFrom September to October 2017, 107 participants (51% males), 78 in 2D group and 29 in 3D group were enrolled. Median age was 5.8 years (IQR 4.4–7.3). All participants had RVNA titers ≥0.5 IU/ml after primary vaccination [GMT 2D: 18.6 (95%CI 15.9–21.8) and 3D: 16.3 (95%CI 13.2–20.1 IU/ml), p = 0.35]. At 1-year prior to receiving the booster, only 80% of the children in 2D group maintained RVNA titers ≥0.5 IU/ml compared to 100% of the children in 3D group (p = 0.01). However, all participants in both groups had RVNA ≥0.5 IU/ml at 7-day post booster vaccination [GMT 2D: 20.9 (95%CI 17.4–25.3) and 3D: 22.2 (95%CI 15.8–31.4) IU/ml (P = 0.75)]. The median number of IFN-γ secreting cells at 7-day post-booster dose was 98 and 128 SFCs per 10⁶ PBMCs in the 2D and 3D groups, respectively (P = 0.30).ConclusionsTwo-dose primary rabies immunization provided adequate antibody at post primary vaccination and post booster. The results support 2-dose regimen of pre-exposure rabies immunization in the pediatric population.     

Pertussis epidemiology including direct and indirect effects of the childhood pertussis booster vaccinations,Norway, 1998–2019

BackgroundThe acellular pertussis vaccine has been used in the Norwegian national immunisation program since 1998. Following an increase in pertussis incidence in all age groups, booster doses were introduced for 7–8-year-olds in 2006, and for 15–16-year-olds in 2013. We assessed the effects of the booster doses on pertussis incidence in different age groups to inform potential changes in vaccination policy.MethodsWe included all pertussis cases notified to the Norwegian Surveillance System for Communicable Diseases in 1998–2019. We calculated annual incidence rates (IR, per 100,000 inhabitants) by age group. We estimated average annual changes in IRs (incidence rate ratios, IRR) for each age group for 2006–2012 and 2013–2019 using Poisson regression.ResultsIn 1998–2019, 74,675 cases of pertussis were notified. Coinciding with booster introduction, between 2006 and 2012 the IR decreased among 8–15-year-olds (from 433 to 199/100,000, IRR 0.89 [95% confidence interval 0.88–0.90]). A similar decrease was seen between 2013 and 2019 among 16–19-year-olds (from 171 to 77/100,000, IRR 0.84 [0.82–0.86]). There was no significant change in IRs among children < 1 year of age between 2006 and 2012 (IRR 0.99 [0.95–1.04]) or 2013–2019 (IRR 0.96 [0.91–1.02]). The IR decreased in both periods among adults aged 20–39 and 40+ (IRR 0.94 [0.93–0.95] and 0.92 [0.91–0.92] in 2006–2012; IRR 0.97 [0.96–0.99] and 0.97 [0.96–0.99] in 2013–2019, respectively). Despite steady, high vaccination coverage, in 2013–2019, there was an increase in the IR among children aged 1–7 (63 to 86/100,000, IRR 1.05 [1.03–1.07]) and 8–15 years (88 to 122/100,000, IRR 1.08 [1.06–1.10]).ConclusionsPertussis booster doses have offered direct protection in the targeted age groups. Our findings suggest indirect protection in adults, while the incidence in infants hasn’t changed. The recent increase in IRs among 1–15-year-olds warrants close monitoring and further evaluation of the vaccination schedule.