Estimated COVID-19 vaccine effectiveness against seroconversion from SARS-CoV-2 Infection,March–October, 2021

BackgroundMonitoring the effectiveness of COVID-19 vaccines against SARS-CoV-2 infections remains important to inform public health responses. Estimation of vaccine effectiveness (VE) against serological evidence of SARS-CoV-2 infection might provide an alternative measure of the benefit of vaccination against infection.MethodsWe estimated mRNA COVID-19 vaccine effectiveness (VE) against development of SARS-CoV-2 anti-nucleocapsid antibodies in March–October 2021, during which the Delta variant became predominant. Participants were enrolled from four participating healthcare systems in the United States, and completed electronic surveys that included vaccination history. Dried blood spot specimens collected on a monthly basis were analyzed for anti-spike antibodies, and, if positive, anti-nucleocapsid antibodies. We used detection of new anti-nucleocapsid antibodies to indicate SARS-CoV-2 infection, and estimated VE by comparing 154 case-participants with new detection of anti-nucleocapsid antibodies to 1,540 seronegative control-participants matched by calendar period. Using conditional logistic regression, we estimated VE ≥ 14 days after the 2nd dose of an mRNA vaccine compared with no receipt of a COVID-19 vaccine dose, adjusting for age group, healthcare worker occupation, urban/suburban/rural residence, healthcare system region, and reported contact with a person testing positive for SARS-CoV-2.ResultsAmong individuals who completed a primary series, estimated VE against seroconversion from SARS-CoV-2 infection was 88.8% (95% confidence interval [CI], 79.6%–93.9%) after any mRNA vaccine, 87.8% (95% CI, 75.9%–93.8%) after BioNTech vaccine and 91.7% (95% CI, 75.7%–97.2%) after Moderna vaccine. VE was estimated to be lower ≥ 3 months after dose 2 compared with < 3 months after dose 2, and among participants who were older or had underlying health conditions, although confidence intervals overlapped between subgroups.ConclusionsVE estimates generated using infection-induced antibodies were consistent with published estimates from clinical trials and observational studies that used virologic tests to confirm infection during the same period. Our findings support recommendations for eligible adults to remain up to date with COVID-19 vaccination.     

Safety of simultaneous vaccination with COVID-19 vaccines in the Vaccine Safety Datalink

IntroductionSafety data on simultaneous vaccination (SV) with primary series monovalent COVID-19 vaccines and other vaccines are limited. We describe SV with primary series COVID-19 vaccines and assess 23 pre-specified health outcomes following SV among persons aged ≥5 years in the Vaccine Safety Datalink (VSD).MethodsWe utilized VSD’s COVID-19 vaccine surveillance data from December 11, 2020-May 21, 2022. Analyses assessed frequency of SV. Rate ratios (RRs) were estimated by Poisson regression when the number of outcomes was ≥5 across both doses, comparing outcome rates between COVID-19 vaccinees receiving SV and COVID-19 vaccinees receiving no SV in the 1–21 days following COVID-19 vaccine dose 1 and 1–42 days following dose 2 by SV type received (“All SV”, “Influenza SV”, “Non-influenza SV”).ResultsSV with COVID-19 vaccines was not common practice (dose 1: 0.7 % of 8,455,037 persons, dose 2: 0.3 % of 7,787,013 persons). The most frequent simultaneous vaccines were influenza, HPV, Tdap, and meningococcal. Outcomes following SV with COVID-19 vaccines were rare (total of 56 outcomes observed after dose 1 and dose 2). Overall rate of outcomes among COVID-19 vaccinees who received SV was not statistically significantly different than the rate among those who did not receive SV (6.5 vs. 6.8 per 10,000 persons). Statistically significant elevated RRs were observed for appendicitis (2.09; 95 % CI, 1.06–4.13) and convulsions/seizures (2.78; 95 % CI, 1.10–7.06) in the “All SV” group following dose 1, and for Bell’s palsy (2.82; 95 % CI, 1.14–6.97) in the “Influenza SV” group following dose 2.ConclusionCombined pre-specified health outcomes observed among persons who received SV with COVID-19 vaccine were rare and not statistically significantly different compared to persons who did not receive SV with COVID-19 vaccine. Statistically significant adjusted rate ratios were observed for some individual outcomes, but the number of outcomes was small and there was no adjustment for multiple testing.     

Effectiveness of adenovirus type 5 vectored and inactivated COVID-19 vaccines against symptomatic COVID-19, COVID-19 pneumonia,and severe COVID-19 caused by the B.1.617.2 (Delta) variant: Evidence from an outbreak in Yunnan,China, 2021

BackgroundIn partial response to the coronavirus disease 2019 (COVID-19) pandemic, countries around the world are conducting large-scale vaccination campaigns. Real-world estimates of vaccine effectiveness (VE) against the B.1.617.2 (Delta) variant are still limited. An outbreak in Ruili city of China provided an opportunity to evaluate VE against the Delta variant of two types of COVID-19 vaccines in use in China and globally – inactivated (CoronaVac and BBIBP-CorV) and adenovirus type 5 vectored (Convidecia) vaccines.MethodsWe estimated VE using a retrospective cohort study two months after the Ruili vaccination campaign (median: 63 days). Close contacts of infected people (Chinese nationality, 18 years and above) were included to assess VE against symptomatic Covid-19, COVID-19 pneumonia, and severe COVID-19. We calculated the relative risks (RR) of the outcomes for unvaccinated compared with fully vaccinated individuals. We used logistic regression analyses to estimate adjusted VEs, controlling for gender and age group (18–59 years and 60 years and over).We compared unvaccinated and fully vaccinated individuals on duration of RT-PCR positivity and Ct value.FindingsThere were 686 close contacts eligible for VE estimates. Adjusted VE of ad5-vectored vaccine was 61.5% (95% CI, 9.5–83.6) against symptomatic COVID-19, 67.9% (95%CI: 1.7–89.9) against pneumonia, and 100% (95%CI: 36.6–100) against severe/critical illness. For the two inactivated vaccines, combined VE was 74.6% (95% CI, 36.0–90.0) against symptomatic COVID-19, 76.7% (95% CI: 19.3–93.3) against pneumonia, and 100% (95% CI: 47.6–100) against severe/critical COVID-19. There were no statistically significant differences in VE between two inactivated vaccines for symptomatic COVID-19 and for pneumonia, nor were there statistically significant differences between inactivated and ad5-vectored VE in any of the three outcomes. The median durations of RT-PCR positivity were 17 days for fifteen people vaccinated with an inactivated vaccine, 18 days for forty-four people vaccinated with the Ad5 vectored vaccine, and 26 days for eleven unvaccinated individuals. InterpretationThese results provide reassuring evidence that the three vaccines are effective at preventing Delta-variant COVID-19 in short term following vaccination campaign, and are most effective at preventing more serious illness. The findings of reduced duration of RT-PCR positivity and length of hospital stay associated with full vaccination suggests potential saving of health-care system resources.     

Comparison of mRNA vaccine effectiveness against COVID-19-associated hospitalization by vaccination source: Immunization information systems,electronic medical records,and self-report—IVY Network,February 1–August 31, 2022

BackgroundAccurate determination of COVID-19 vaccination status is necessary to produce reliable COVID-19 vaccine effectiveness (VE) estimates. Data comparing differences in COVID-19 VE by vaccination sources (i.e., immunization information systems [IIS], electronic medical records [EMR], and self-report) are limited. We compared the number of mRNA COVID-19 vaccine doses identified by each of these sources to assess agreement as well as differences in VE estimates using vaccination data from each individual source and vaccination data adjudicated from all sources combined.MethodsAdults aged ≥18 years who were hospitalized with COVID-like illness at 21 hospitals in 18 U.S. states participating in the IVY Network during February 1–August 31, 2022, were enrolled. Numbers of COVID-19 vaccine doses identified by IIS, EMR, and self-report were compared in kappa agreement analyses. Effectiveness of mRNA COVID-19 vaccines against COVID-19-associated hospitalization was estimated using multivariable logistic regression models to compare the odds of COVID-19 vaccination between SARS-CoV-2-positive case-patients and SARS-CoV-2-negative control-patients. VE was estimated using each source of vaccination data separately and all sources combined.ResultsA total of 4499 patients were included. Patients with ≥1 mRNA COVID-19 vaccine dose were identified most frequently by self-report (n = 3570, 79 %), followed by IIS (n = 3272, 73 %) and EMR (n = 3057, 68 %). Agreement was highest between IIS and self-report for 4 doses with a kappa of 0.77 (95 % CI = 0.73–0.81). VE point estimates of 3 doses against COVID-19 hospitalization were substantially lower when using vaccination data from EMR only (VE = 31 %, 95 % CI = 16 %–43 %) than when using all sources combined (VE = 53 %, 95 % CI = 41 %–62%).ConclusionVaccination data from EMR only may substantially underestimate COVID-19 VE.     

Effectiveness of Covid-19 vaccines against symptomatic and asymptomatic SARS-CoV-2 infections in an urgent care setting

BackgroundIt is critical to monitor changes in vaccine effectiveness against COVID-19 outcomes for various vaccine products in different population subgroups.MethodsWe conducted a retrospective study in patients ≥12 years who underwent testing for SARS-CoV-2 virus from April 14 through October 25, 2021, at urgent care centers in the New York metropolitan area. Patients self-reported vaccination status at the time of testing. We used a test-negative design to estimate vaccine effectiveness (VE) by comparing odds of a positive test for SARS-CoV-2 infection among vaccinated (n = 474,805), partially vaccinated (n = 87,834), and unvaccinated (n = 369,333) patients, adjusted for demographic factors and calendar time.ResultsVE against symptomatic infection after 2 doses of mRNA vaccine was 96% (95% Confidence Interval: 95%, 97%) in the pre-delta period and reduced to 79% (95% CI: 77%, 81%) in the delta period. In the delta period, VE for 12–15-year-olds (85%; [95% CI: 81%, 88%]) was higher compared to older age groups (<65% for all other age groups). VE estimates did not differ by sex and race/ethnicity. VE against symptomatic infection was the highest for individuals with a prior infection followed by full vaccination. VE against symptomatic infection after the 2-dose mRNA-1273 vaccine (82% [95% CI: 80%, 84%]) was higher compared to the BNT162b2 vaccine (76% [95% CI: 74%, 78%]) in the delta period. VE after 1-dose of the Ad26.COV2.S vaccine was the lowest compared to other vaccines (19% [95% CI: 15%, 23%]) in the delta period.ConclusionsVE against infection after two doses of the mRNA vaccines was high initially, but significantly reduced against the delta variant for both FDA-approved vaccines.     

Seropositivity to Nucleoprotein to detect mild and asymptomatic SARS-CoV-2 infections: A complementary tool to detect breakthrough infections after COVID-19 vaccination?

BackgroundWith COVID-19 vaccine roll-out ongoing in many countries globally, monitoring of breakthrough infections is of great importance. Antibodies persist in the blood after a severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. Since COVID-19 vaccines induce immune response to the Spike protein of the virus, which is the main serosurveillance target to date, alternative targets should be explored to distinguish infection from vaccination.MethodsMultiplex immunoassay data from 1,513 SARS-CoV-2 RT-qPCR-tested individuals (352 positive and 1,161 negative) without COVID-19 vaccination history were used to determine the accuracy of Nucleoprotein-specific immunoglobulin G (IgG) in detecting past SARS-CoV-2 infection. We also described Spike S1 and Nucleoprotein-specific IgG responses in 230 COVID-19 vaccinated individuals (Pfizer/BioNTech).ResultsThe sensitivity of Nucleoprotein seropositivity was 85% (95% confidence interval: 80–90%) for mild COVID-19 in the first two months following symptom onset. Sensitivity was lower in asymptomatic individuals (67%, 50–81%). Participants who had experienced a SARS-CoV-2 infection up to 11 months preceding vaccination, as assessed by Spike S1 seropositivity or RT-qPCR, produced 2.7-fold higher median levels of IgG to Spike S1 ≥ 14 days after the first dose as compared to those unexposed to SARS-CoV-2 at ≥ 7 days after the second dose (p = 0.011). Nucleoprotein-specific IgG concentrations were not affected by vaccination in infection-naïve participants.ConclusionsSerological responses to Nucleoprotein may prove helpful in identifying SARS-CoV-2 infections after vaccination. Furthermore, it can help interpret IgG to Spike S1 after COVID-19 vaccination as particularly high responses shortly after vaccination could be explained by prior exposure history.     

Vaccine effectiveness and duration of protection of COVID-19 mRNA vaccines against Delta and Omicron BA.1 symptomatic and severe COVID-19 outcomes in adults aged 50 years and over in France

The emergence of SARS-CoV-2 variants calls for continuous monitoring of vaccine effectiveness (VE). We estimated the absolute effectiveness of complete 2-dose primary vaccination and booster vaccination with COVID-19 mRNA vaccines, and the duration of protection against Delta and Omicron BA.1 symptomatic infection and severe outcomes. French residents aged ≥50 years, who presented with SARS-CoV-2-like symptoms and tested for SARS-CoV-2 between June 6, 2021 and February 10, 2022 were included. A test-negative study was conducted to estimate VE against symptomatic infection, using conditional logistic regression models. Cox proportional hazard regressions were performed to assess additional protection against severe COVID-19 outcomes (any hospitalization, and intensive care units [ICU] admission or in-hospital death). In total, 273 732 cases and 735 919 controls were included. VE against symptomatic infection after 2-doses vaccination was 86% (95% CI: 75–92%) for Delta and 70% (58–79%) for Omicron, 7–30 days post vaccination. Protection waned over time, reaching 60% (57–63%) against Delta and 20% (16.–24%) for Omicron BA.1 > 120 days after vaccination. The booster dose fully restored protection against symtpomatic Delta infection (95% [81–99%]) but only partially against symptomatic Omicron BA.1 infection (63% [59–67%]). VE against Delta-related severe outcomes was above 95% with 2 doses, and persisted for at least four months. Protection against any Omicron BA.1-hospitalization was 92% (65%-99%) at 8–30 days, and 82% (67%-91%) > 120 days from the second dose. Against BA.1 ICU admission or in-patient death, VE stood at 98% (0–100%) at 8–30 days, and was 90% (40–99%) > 120 days from the second dose. Protection confered by mRNA vaccines against severe disease caused by either Delta or Omicron BA.1 appeared high and sustained over time. Protection against symptomatic diseases after 2 doses decreased rapidly, especially against Omicron BA.1. A booster dose restored high protection against Delta but only a partial one against Omicron BA.1.     

Relative effectiveness of a 2nd booster dose of COVID-19 mRNA vaccine up to four months post administration in individuals aged 80 years or more in Italy: A retrospective matched cohort study

Several countries started a 2nd booster COVID-19 vaccination campaign targeting the elderly population, but evidence around its effectiveness is still scarce. This study aims to estimate the relative effectiveness of a 2nd booster dose of COVID-19 mRNA vaccine in the population aged ≥ 80 years in Italy, during predominant circulation of the Omicron BA.2 and BA.5 subvariants.We linked routine data from the national vaccination registry and the COVID-19 surveillance system. On each day between 11 April and 6 August 2022, we matched 1:1, according to several demographic and clinical characteristics, individuals who received the 2nd booster vaccine dose with individuals who received the 1st booster vaccine dose at least 120 days earlier. We used the Kaplan-Meier method to compare the risks of SARS-CoV-2 infection and severe COVID-19 (hospitalisation or death) between the two groups, calculating the relative vaccine effectiveness (RVE) as (1 – risk ratio)X100.Based on the analysis of 831,555 matched pairs, we found that a 2nd booster dose of mRNA vaccine, 14–118 days post administration, was moderately effective in preventing SARS-CoV-2 infection compared to a 1st booster dose administered at least 120 days earlier [14.3 %, 95 % confidence interval (CI): 2.2–20.2]. RVE decreased from 28.5 % (95 % CI: 24.7–32.1) in the time-interval 14–28 days to 7.6 % (95 % CI: ?14.1 to 18.3) in the time-interval 56–118 days. However, RVE against severe COVID-19 was higher (34.0 %, 95 % CI: 23.4–42.7), decreasing from 43.2 % (95 % CI: 30.6–54.9) to 27.2 % (95 % CI: 8.3–42.9) over the same time span.Although RVE against SARS-CoV-2 infection was much reduced 2–4 months after a 2nd booster dose, RVE against severe COVID-19 was about 30 %, even during prevalent circulation of the Omicron BA.5 subvariant. The cost-benefit of a 3rd booster dose for the elderly people who received the 2nd booster dose at least four months earlier should be carefully evaluated.     

Effectiveness of the COVID-19 vaccines on preventing symptomatic SARS-CoV-2 infections and hospitalizations in Southwestern Alaska,January–December 2021

The population in rural southwest Alaska has been disproportionately affected by COVID-19. To assess the benefit of COVID-19 vaccines, we analyzed data from the regional health system. We estimated vaccine effectiveness (VE) during January 16–December 3, 2021, against symptomatic SARS-CoV-2 infection after a primary series or booster dose, and overall VE against hospitalization. VE of a primary series against symptomatic infection among adult residents was 91.3% (95% CI: 85.7, 95.2) during January 16–May 7, 2021, 50.3% (95% CI, 41.1%–58.8%) during July 17–September 24, and 37.0% (95% CI, 27.8–45.0) during September 25–December 3, 2021; VE of a booster dose during September 25–December 3, 2021, was 92.1% (95% CI: 87.2–95.2). During the overall study period, VE against hospitalization was 91.9% (95% CI: 85.4–95.5). COVID-19 vaccination offered strong protection against hospitalization and a booster dose restored protection against symptomatic infection.     

Protective immune responses against Haemophilus influenzae type b elicited by a fully-liquid DTaP-IPV-Hib-HepB vaccine (VAXELIS™)

BackgroundDTaP-IPV-Hib-HepB is a fully-liquid, hexavalent combination vaccine (Vaxelis?) approved for vaccination against diphtheria, tetanus, pertussis, poliomyelitis, hepatitis B, and invasive disease due to Haemophilus influenzae type b (Hib). Hib capsular polysaccharide, polyribosylribitol phosphate (PRP), is conjugated to Neisseria meningitidis outer membrane protein complex (OMPC). Safety and immunogenicity of DTaP-IPV-Hib-HepB were evaluated in 6 Phase III clinical studies including > 5,200 children. Studies included vaccination schedules in the United States (2, 4, 6 months of age) and Europe (2, 3, 4, 12 months of age and 2,4,11–12 months of age).MethodsData pertaining to anti-PRP responses of DTaP-IPV-Hib-Hep B compared to control vaccines from 5 Phase III studies are summarized.ResultsPost-infant series, the percentage of participants that achieved protective antibody thresholds for PRP (anti-PRP titer ≥ 0.15 μg/mL and ≥ 1.0 μg/mL, respectively) were higher in DTaP-IPV-Hib-HepB recipients compared to recipients who received control vaccines. A high level of protective responses (96.6% at ≥ 0.15 μg/mL [95% CI:94.8, 97.9%]; 72.9% at ≥ 1.0 μg/mL [95% CI:69.2,76.4%]) were seen post-dose 2 of the 2 + 1 vaccination schedule and met superiority criteria over comparator, p-value < 0.001.In the same schedule, prior to administration of the toddler dose (in the second year of life), anti-PRP titers were higher in DTaP-IPV-Hib-HepB recipients (91.4% at ≥ 0.15 μg/mL; 46.8% at ≥ 1.0 μg/mL) as compared to recipients who received control vaccines (63.4% at ≥ 0.15 μg/mL; 17.1% at ≥ 1.0 μg/mL).One-month post-toddler dose, high levels of anti-PRP titers were achieved in both DTaP-IPV-Hib-HepB recipients (99.8% at ≥ 0.15 μg/mL; 96.6% at ≥ 1.0 μg/mL) and recipients who received control vaccines (99.5% at ≥ 0.15 μg/mL; 94.9% at ≥ 1.0 μg/mL).ConclusionsThese results support that DTaP-IPV-Hib-HepB induces a robust and sustained early Hib response. During the high-risk period for Hib disease after the infant vaccine and prior to the toddler dose; >90% of recipients maintained superior protective anti-PRP levels compared to control.     

Effectiveness of COVID-19 vaccines at preventing emergency department or urgent care encounters and hospitalizations among immunocompromised adults: An observational study of real-world data across 10 US states from August-December 2021

BackgroundImmunocompromised (IC) persons are at increased risk for severe COVID-19 outcomes and are less protected by 1–2 COVID-19 vaccine doses than are immunocompetent (non-IC) persons. We compared vaccine effectiveness (VE) against medically attended COVID-19 of 2–3 mRNA and 1–2 viral-vector vaccine doses between IC and non-IC adults.MethodsUsing a test-negative design among eight VISION Network sites, VE against laboratory-confirmed COVID-19–associated emergency department (ED) or urgent care (UC) events and hospitalizations from 26 August-25 December 2021 was estimated separately among IC and non-IC adults and among specific IC condition subgroups. Vaccination status was defined using number and timing of doses. VE for each status (versus unvaccinated) was adjusted for age, geography, time, prior positive test result, and local SARS-CoV-2 circulation.ResultsWe analyzed 8,848 ED/UC events and 18,843 hospitalizations among IC patients and 200,071 ED/UC events and 70,882 hospitalizations among non-IC patients. Among IC patients, 3-dose mRNA VE against ED/UC (73% [95% CI: 64–80]) and hospitalization (81% [95% CI: 76–86]) was lower than that among non-IC patients (ED/UC: 94% [95% CI: 93–94]; hospitalization: 96% [95% CI: 95–97]). Similar patterns were observed for viral-vector vaccines. Transplant recipients had lower VE than other IC subgroups.ConclusionsDuring B.1.617.2 (Delta) variant predominance, IC adults received moderate protection against COVID-19–associated medical events from three mRNA doses, or one viral-vector dose plus a second dose of any product. However, protection was lower in IC versus non-IC patients, especially among transplant recipients, underscoring the need for additional protection among IC adults.     

Effectiveness of quadrivalent influenza vaccination in the first year of a funded childhood program in Queensland,Australia, 2018

BackgroundFollowing high influenza activity in 2017, the state of Queensland, Australia, funded a quadrivalent inactivated influenza vaccination program for children aged 6 months to <5 years in 2018. We calculated influenza vaccine effectiveness (VE) among children eligible for this program.MethodsA matched case-control study was conducted. Cases were identified using Queensland 2018 influenza notification data among children age-eligible for funded vaccination. Controls were drawn from Australian Immunisation Register records of Queensland resident children age-eligible for funded influenza vaccine. Up to 10 controls per case were matched for location and birthdate. First dose vaccination was valid if received ≥14 days prior to specimen collection; a second dose was valid if received ≥28 days after first dose receipt. VE was calculated for vaccine doses and adherence to national recommendations for two doses in the first season (schedule completeness) and adjusted (VE_adj) for sex and First Nations status.ResultsThere were 1,125 cases and 10,645 matched controls analysed. Overall VE_adj against laboratory-confirmed influenza was 51% (95% confidence interval (CI) 41–60). VE_adj was 60% (95% CI 46–70) for children who received two doses in 2018, and 60% (95% CI 48–69) for children vaccinated appropriately according to schedule completeness. VE increased with age.ConclusionsModerate vaccine effectiveness was observed for children eligible for the funded program in Queensland in 2018, adding to the sparse evidence for influenza vaccine use in Australian children. Adhering to the national first season two dose schedule for influenza vaccine receipt in children ensures maximum protection.     

COVID-19 outbreak in an elderly care home: Very low vaccine effectiveness and late impact of booster vaccination campaign

BackgroundElderly people in long-term care facilities (LTCF) are at higher risk for (severe) COVID-19, yet evidence of vaccine effectiveness (VE) in this population is scarce. In November 2021 (Delta period), a COVID-19 outbreak occurred at a LTCF in the Netherlands, continuing despite measures and booster vaccination campaign. We investigated the outbreak to assess VE of primary COVID-19 vaccination against SARS-CoV-2 infection and mortality, and to describe the impact of the booster vaccination.MethodsWe calculated attack rate (AR) and case fatality (CF) per vaccination status (unvaccinated, primarily vaccinated and boostered). We calculated VE – at on average 6 months after vaccination – as 1- risk ratio (RR) using the crude risk ratio (RR) with 95% confidence intervals (CI) for the association between vaccination status (primary vaccination versus unvaccinated) and outcomes (SARS-CoV-2 infection and mortality < 30 days after testing positive for SARS-CoV-2).ResultsThe overall AR was 67% (70/105). CF was 33% (2/6) among unvaccinated cases, 12% among primarily vaccinated (7/58) and 0% (0/5) among boostered. The VE of primary vaccination was 17% (95% CI ?28%; 46%) against SARS-CoV-2 infection and 70% (95% CI ?44%; 96%) against mortality. Among boostered residents (N = 55), there were 25 cases in the first week after receiving the booster dose, declining to 5 in the second and none in the third week.ConclusionVE of primary vaccination in residents of LTCF was very low against SARS-CoV-2 infection and moderate against mortality. There were few cases at 2 weeks after the booster dose and no deaths, despite the presence of susceptible residents. These data are consistent with the positive impact of the booster vaccination in curbing transmission. Timely booster vaccination in residents of LTCF is therefore important.     

Effectiveness of full (booster) COVID-19 vaccination against severe outcomes and work absenteeism in hospitalized patients with COVID-19 during the Delta and Omicron waves in Greece

AimWe estimated vaccine effectiveness (VE) of full (booster) vaccination against severe outcomes in hospitalized COVID-19 patients during the Delta and Omicron waves.MethodsThe study extended from November 15, 2021 to April 17, 2022. Full vaccination was defined as a primary vaccination plus a booster ≥ 6 months later.ResultsWe studied 1138 patients (mean age: 66.6 years), of whom 826 (72.6 %) had ≥ 1 comorbidity. Of the 1138 patients, 75 (6.6 %) were admitted to intensive care unit (ICU), 64 (5.6 %) received mechanical ventilation, and 172 (15.1 %) died. There were 386 (33.9 %) fully vaccinated, 172 (15.1 %) partially vaccinated, and 580 (51 %) unvaccinated patients. Unvaccinated patients were absent from work for longer periods compared to partially or fully vaccinated patients (mean absence of 20.1 days versus 12.3 and 17.3 days, respectively; p-value = 0.03). Compared to unvaccinated patients, fully vaccinated patients were less likely to be admitted to ICU [adjusted relative risk (ARR: 0.49; 95 % CI: 0.29–0.84)], mechanically ventilated (ARR: 0.43; 95 % CI: 0.23–0.80), and die (ARR: 0.57; 95 % CI: 0.42–0.78), while they were hospitalized for significantly shorter periods (ARR: 0.79; 95 % CI: 0.70–0.89). The adjusted full VE was 48.8 % (95 % CI: 42.7 %-54.9 %) against ICU admission, 55.4 % (95 % CI: 52.0 %-56.2 %) against mechanical ventilation, and 22.6 % (95 % CI: 7.4 %-34.8 %) against death. For patients with ≥ 3 comorbidities, VE was 56.2 % (95 % CI: 43.9 %-67.1 %) against ICU admission, 60.2 % (95 % CI: 53.7 %-65.4 %) against mechanical ventilation, and 43.9 % (95 % CI: 19.9 %-59.7 %) against death.ConclusionsFull (booster) COVID-19 vaccination conferred protection against severe outcomes, prolonged hospitalization, and prolonged work absenteeism.     

Vaccine-induced seroconversion in participants in the North Carolina COVID-19 community Research Partnership

Well-regulated clinical trials have shown FDA-approved COVID-19 vaccines to be immunogenic and highly efficacious. We evaluated seroconversion rates in adults reporting ≥ 1 dose of an mRNA COVID-19 vaccine in a cohort study of nearly 8000 adults residing in North Carolina to validate immunogenicity using a novel approach: at-home, participant administered point-of-care testing. Overall, 91.4% had documented seroconversion within 75 days of first vaccination (median: 31 days). Participants who were older and male participants were less likely to seroconvert (adults aged 41–65: adjusted hazard ratio [aHR] 0.69 [95% confidence interval (CI): 0.64, 0.73], adults aged 66–95: aHR 0.55 [95% CI: 0.50, 0.60], compared to those 18–40; males: aHR 0.92 [95% CI: 0.87, 0.98], compared to females). Participants with evidence of prior infection were more likely to seroconvert than those without (aHR 1.50 [95% CI: 1.19, 1.88]) and those receiving BNT162b2 were less likely to seroconvert compared to those receiving mRNA-1273 (aHR 0.84 [95% CI: 0.79, 0.90]). Reporting at least one new symptom after first vaccination did not affect time to seroconversion, but participants reporting at least one new symptom after second vaccination were more likely to seroconvert (aHR 1.11 [95% CI: 1.05, 1.17]). This data demonstrates the high community-level immunogenicity of COVID-19 vaccines, albeit with notable differences in older adults, and feasibility of using at-home, participant administered point-of-care testing for community cohort monitoring.Trial registration: ClinicalTrials.gov NCT04342884.     

Inactive SARS-CoV-2 vaccine generates high antibody responses in healthcare workers with and without prior infection

Background and ObjectivesHealthcare workers (HCWs) were among the first groups to be vaccinated in Turkey. The data to be obtained by the vaccination of HCWs would guide wide spread vaccination programs.Materials and MethodsThe study included 330 HCWs working at Istanbul University-Cerrahpa?a, Cerrahpa?a Medical Faculty Hospital and vaccinated with inactive CoronaVac (Sinovac Life Sciences, China) SARS-CoV-2 vaccine in two doses (28 days apart). Anti-Spike /RBD IgG levels were measured 14 days after the first dose and 28 days after the second dose. Chemiluminescent microparticle immunoassay (CMIA) (ARCHITECT IgG II Quant test, Abbott, USA), which is 100% compatible with plaque reduction neutralization test (PRNT), was used.ResultsOf the participants, 211 (63.9%) were female, 119 (36.1%) were male, and mean age was 39.6 ± 7.7 years. In those without prior COVID-19 history; (n = 255) antibody positivity was detected as 48.2% (95% CI: 42.1–54.3) 14 days after the first dose of vaccine, and 99.2% (95% CI: 98.1–100) at day 28 after the second dose. Antibody titers were significantly lower in patients with hypertension (p = 0.011). In those with prior history of COVID-19 (n = 75); both the antibody positivity rates after the first vaccine (48.2% vs 100%, p = 0.000) and the anti-spike/RBD antibody levels after the second vaccine (with a ≥ 1050 AU/mL titer equivalent to PRNT 1/80 dilution) was significant than infection-naive group (25.9% vs. 54.7%, p = 0.000). Antibody positivity after two doses of vaccination for all study group was 99.4% (95% CI: 98.6–100).ConclusionsTwo doses CoronaVac produce effective humoral immunity in HCWs. Antibody response is significantly higher in those with prior history of COVID-19 than infection-naive group. Given no significant benefit of the second dose, a single shot of vaccination may be sufficient for those with prior history of COVID-19. Monitoring humoral and cellular immune responses, considering new variants, is required to validate this approach.     

Effectiveness of vaccines in preventing hospitalization due to COVID-19: A multicenter hospital-based case-control study,Germany, June 2021 to January 2022

We included 852 patients in a prospectively recruiting multicenter matched case-control study in Germany to assess vaccine effectiveness (VE) in preventing COVID-19-associated hospitalization during the Delta-variant dominance. The two-dose VE was 89 % (95 % CI 84–93 %) overall, 79 % in patients with more than two comorbidities and 77 % in adults aged 60–75 years. A third dose increased the VE to more than 93 % in all patient-subgroups.     

Acute reactions after a homologous primary COVID-19 vaccination series: Analysis of Taiwan V-Watch data

IntroductionThe ChAdOx1 nCoV-19 (ChAd), mRNA-1273 (m1273), MVC-COV1901 (MVC), and BNT162b2 (BNT) COVID-19 vaccines received authorization for emergency use in Taiwan beginning in February 2021. We investigated acute reactions to homologous primary COVID-19 vaccination series in adults aged ≥ 18 years.MethodsIn this prospective observational study based on smartphone data (Taiwan V-Watch), we calculated the frequencies of self-reported local and systemic acute reactions within 7 days of a COVID-19 vaccination, and the health effects up to 3 weeks after each dose. Those who reported adverse reactions after both doses were assessed by the McNemar test.ResultsDuring 22 March 2021–13 December 2021, 77,468 adults were enrolled; 59.0 % were female and 77.8 % were aged 18–49 years. For both doses of all four vaccines, the local and systemic reactions were minor in severity and highest on days 1 and 2 after vaccination, and declined markedly until day 7. For 65,367 participants who provided data after the first and second doses, systemic reactions were more frequent after dose 2 of the BNT and m1273 vaccines (McNemar tests: both p < 0.001), while local reactions were more frequent after dose 2 of the m1273 and MVC vaccines (both p < 0.001), compared with dose 1 of the homologous vaccine. Among the participants aged 18–49 years, the percentage who missed work on the day after vaccination was slightly higher among women (9.3 %) than among men (7.0 %).ConclusionsAcute reactogenicity and impact of work absenteeism for the four COVID vaccines in the V-Watch survey were mild and of short duration.     

Risk of serious adverse events after the BNT162b2, CoronaVac,and ChAdOx1 vaccines in Malaysia: A self-controlled case series study

BackgroundRapid deployment of COVID-19 vaccines is challenging for safety surveillance, especially on adverse events of special interest (AESIs) that were not identified during the pre-licensure studies. This study evaluated the risk of hospitalisations for predefined diagnoses among the vaccinated population in Malaysia.MethodsHospital admissions for selected diagnoses between 1 February 2021 and 30 September 2021 were linked to the national COVID-19 immunisation register. We conducted self-controlled case-series study by identifying individuals who received COVID-19 vaccine and diagnosis of thrombocytopenia, venous thromboembolism, myocardial infarction, myocarditis/pericarditis, arrhythmia, stroke, Bell’s Palsy, and convulsion/seizure. The incidence of events was assessed in risk period of 21 days postvaccination relative to the control period. We used conditional Poisson regression to calculate the incidence rate ratio (IRR) and 95% confidence interval (CI) with adjustment for calendar period.ResultsThere was no increase in the risk for myocarditis/pericarditis, Bell’s Palsy, stroke, and myocardial infarction in the 21 days following either dose of BNT162b2, CoronaVac, and ChAdOx1 vaccines. A small increased risk of venous thromboembolism (IRR 1.24; 95% CI 1.02, 1.49), arrhythmia (IRR 1.16, 95% CI 1.07, 1.26), and convulsion/seizure (IRR 1.26; 95% CI 1.07, 1.48) was observed among BNT162b2 recipients. No association between CoronaVac vaccine was found with all events except arrhythmia (IRR 1.15; 95% CI 1.01, 1.30). ChAdOx1 vaccine was associated with an increased risk of thrombocytopenia (IRR 2.67; 95% CI 1.21, 5.89) and venous thromboembolism (IRR 2.22; 95% CI 1.17, 4.21).ConclusionThis study shows acceptable safety profiles of COVID-19 vaccines among recipients of BNT162b2, CoronaVac, and ChAdOx1 vaccines. This information can be used together with effectiveness data for risk-benefit analysis of the vaccination program. Further surveillance with more data is required to assess AESIs following COVID-19 vaccination in short- and long-term.