Parent perspectives on childhood vaccination: How to deal with vaccine hesitancy and refusal?

Background

The aims of the study are to evaluate attitudes about childhood vaccines and vaccine refusal or delay among parents and to assess the role played by the variables mapped as potential determinants to suggest strategies that could improve childhood vaccination rates.

Association of vaccine hesitancy and immunization coverage rates in the European Union

While previous studies have validated vaccine hesitancy scales with uptake behavior at the individual level, the conditions under which aggregated survey data are useful are less clear. We show that vaccine public opinion data aggregated at the subnational level can serve as a valid indicator of aggregate vaccine behaviour. We use a public opinion survey (Eurobarometer EB 91.2) with data on vaccine hesitancy for the EU in 2019. We link this information to (subnational) regional immunization coverage rates for childhood vaccines – DTP3, MCV1, and MCV2 -- obtained from the WHO for 2019. We conduct multilevel regression analyses with data for 177 regions in 20 countries. Given the variation in vaccine hesitancy and immunization rates between countries and within countries, we affirm the valuable role that surveys can play as a public health surveillance tool when it comes to vaccine behavior. We find statistically significantly lower regional vaccine immunization rates in regions where vaccine hesitancy is more pronounced. Our results suggest that different uptake rates across subnational regions are due, at least in part, to differences in attitudes towards vaccines and vaccination. The results are robust to several alternative specifications.     

Factors influencing Covid-19 vaccine acceptance across subgroups in the United States: Evidence from a conjoint experiment

Public health officials warn that the greatest barrier to widespread vaccination against Covid-19 will not be scientific or technical, but the considerable public hesitancy to take a novel vaccine. Understanding the factors that influence vaccine acceptance is critical to informing public health campaigns aiming to combat public fears and ensure broad uptake. Employing a conjoint experiment embedded on an online survey of almost 2,000 adult Americans, we show that the effects of seven vaccine attributes on subjects’ willingness to vaccinate vary significantly across subgroups. Vaccine efficacy was significantly more influential on vaccine acceptance among whites than among Blacks, while bringing a vaccine to market under a Food and Drug Administration Emergency Use Authorization had a stronger adverse effect on willingness to vaccinate among older Americans and women. Democrats were more sensitive to vaccine efficacy than Republicans, and both groups responded differently to various endorsements of the vaccine. We also explored whether past flu vaccination history, attitudes toward general vaccine safety, and personal contact with severe cases of Covid-19 can explain variation in group vaccination hesitancy. Many subgroups that exhibit the greatest Covid-19 vaccine hesitancy did not report significantly lower frequencies of flu vaccination. Several groups that exhibited greater Covid-19 vaccine hesitancy also reported greater concerns about vaccine safety generally, but others did not. Finally, subgroup variation in reported personal contact with severe cases of Covid-19 did not strongly match subgroup variation in vaccine acceptance.     

Two media-reported vaccine events in China from 2013 to 2016: Impact on confidence and vaccine utilization

BackgroundChina media reported infant deaths following hepatitis B vaccination in late 2013, leading to temporary suspension of hepatitis B vaccine (HepB Event) until the deaths were shown to be coincidental and the vaccine was of standard, good quality. In 2016, a criminal ring in Shandong province that had been purchasing, improperly storing, and reselling Category 2 vaccines (private-sector) to 60 (of 200,000) clinics for 5 years, was exposed, publicized, and prosecuted, and the potential health and epidemiological impacts were investigated to determine whether revaccination was necessary (Shandong Vaccine Event).MethodsWe assessed parental confidence in vaccines through 9 telephone surveys in 6 and 11 provinces before, during, and after the two events. Provider confidence was assessed through in-person interviews following each event. Vaccine utilization was assessed using Immunization Information Management System data from township clinics.ResultsIn the early stages of each event, approximately 30% of parents indicated vaccine hesitancy and 18% said they would refuse routine immunization. Five and nine months after each event, hesitancy and refusal decreased, but not to pre-event levels. During the Shandong Vaccine Event, 49·1% of parents indicated refusal to use Category 2 vaccines; six months later, the rate was 32·8%. Use of HepB decreased by 21% during the first 2 weeks of the HepB Event and by 12·6% during the first 4 weeks of Shandong Vaccine Event, but returned to baseline in less than 3 months. Use of Category 2 vaccine decreased by 49·5% in the first 3 weeks of the Shandong Vaccine Event and by 28·7% 6 months later. After the Shandong Vaccine Event, 64% of clinicians held high confidence in routine immunization, lower than at baseline.ConclusionsThe two events caused mistrust, loss of confidence, and decreases in use of vaccines by parents and providers. In addition to ensuring immunization program integrity, effective communications and ongoing monitoring of vaccine use and confidence should be included to restore confidence and trust in vaccines.     

Older adolescents and young adults willingness to receive the COVID-19 vaccine: Implications for informing public health strategies

ImportanceThe success in ending the COVID-19 pandemic rests partly on the mass uptake of the COVID-19 vaccine. Little work has been done to understand vaccine willingness among older adolescents and young adults. This is important since this age group may be less likely to adhere to public health guidelines.ObjectiveTo understand willingness of getting a vaccine and reasons for vaccine hesitancy among a sample of older adolescents and young adults.DesignData were from the Well-Being and Experiences study (The WE Study), a longitudinal community-based sample of older adolescents and young adults collected from Winnipeg, Manitoba, Canada from 2017 to 2020 (n = 664).SettingThe study setting was a community-based observational longitudinal study.ParticipantsParticipants for the study were aged 14 to 17 years old at baseline in 2016–17 (n = 1000). Data were also collected on one parent/caregiver. Waves 2 (n = 747) and 3 (n = 664) were collected in 2019 and 2020, respectively.ExposuresThe main exposures were sociodemographic factors, health conditions, COVID-19 knowledge, and adversity history.Main OutcomesThe main outcomes were COVID-19 vaccine willingness, hesitancy, and reasons for hesitancy.ResultsWillingness to get a COVID-19 vaccine was 65.4%. Willingness did not differ by age, sex, or mental health conditions, but did differ for other sociodemographic characteristics, physical health conditions, COVID-19 knowledge, practicing social/physical distancing, and adversity history. The most common reasons for not wanting a vaccine were related to safety, knowledge, and effectiveness. Sex differences were noted.Conclusions and RelevanceIncreasing uptake of the COVID-19 vaccine among older adolescents and young adults may rely on targeting individuals from households with lower income, financial burden, and adversity history, and generating public health messaging specifically aimed at vaccine safety, how it works to protect against illness, and why it is important to protect oneself against a COVID-19 infection.     

Measuring vaccine hesitancy: Field testing the WHO SAGE Working Group on Vaccine Hesitancy survey tool in Guatemala

BackgroundDespite safe and effective childhood immunizations, decreased acceptance of vaccines has become an emerging global problem. The WHO SAGE Working Group on Vaccine Hesitancy developed a common diagnostic tool, the Vaccine Hesitancy Scale (VHS), to identify and compare hesitancy in different global settings. We field tested the VHS in rural and urban Guatemala.MethodsWe analyzed data from the enrollment visit of a study conducted at four public health clinics in Guatemala. Infants ages 6 weeks-6 months presenting for their first wellness visit were enrolled March-November 2016. Parents completed a demographic survey that included the 10 dichotomous and 10 Likert scale VHS questions. Chi-square or Fisher’s exact for categorical and ANOVA test for continuous variables were used to assess significance levels in survey differences. We conducted a factor analysis to assess the Likert scale questions.ResultsOf 1088 families screened, 871 were eligible and 720 (82.7%) participated. No parent had ever refused a vaccination, and only eight parents (1.1%) had been reluctant or hesitated to get a vaccination for their children. However, only 40.8% (n = 294) of parents said that they think most parents like them have their children vaccinated with all the recommended vaccines. Factor analysis identified two underlying constructs that had eigenvalues of 1.0 or greater and a substantive lack of variability in response across the Likert scale. There were consistent differences between how study clinics responded to the ordinal scaling.ConclusionOur results suggest problems with interpretation of the VHS, especially in the presence of vaccine shortages and using a Likert scale that does not resonate across diverse cultural settings. Our factor analysis suggests that the Likert scale items are more one-dimensional and do not represent the multiple constructs of vaccine hesitancy. We suggest more work is needed to refine this survey for improved reliability and validity.Clinical Trial Registry: NCT02567006.     

Safety of vaccines used for routine immunization in the United States: An updated systematic review and meta-analysis

BackgroundUnderstanding the safety of vaccines is critical to inform decisions about vaccination. Our objective was to conduct a systematic review of the safety of vaccines recommended for children, adults, and pregnant women in the United States.MethodsWe searched the literature in November 2020 to update a 2014 Agency for Healthcare Research and Quality review by integrating newly available data. Studies of vaccines that used a comparator and reported the presence or absence of key adverse events were eligible. Adhering to Evidence-based Practice Center methodology, we assessed the strength of evidence (SoE) for all evidence statements. The systematic review is registered in PROSPERO (CRD42020180089).ResultsOf 56,603 reviewed citations, 338 studies reported in 518 publications met inclusion criteria. For children, SoE was high for no increased risk of autism following measles, mumps, and rubella (MMR) vaccine. SoE was high for increased risk of febrile seizures with MMR. There was no evidence of increased risk of  intussusception with rotavirus vaccine at the latest follow-up (moderate SoE), nor of diabetes (high SoE). There was no evidence of increased risk or insufficient evidence for key adverse events for newer vaccines such as 9-valent human papillomavirus and meningococcal B vaccines. For adults, there was no evidence of increased risk (varied SoE) or insufficient evidence for key adverse events for the new adjuvanted inactivated influenza vaccine and recombinant adjuvanted zoster vaccine. We found no evidence of increased risk (varied SoE) for key adverse events among pregnant women following tetanus, diphtheria, and acellular pertussis vaccine, including stillbirth (moderate SoE).ConclusionsAcross a large body of research we found few associations of vaccines and serious key adverse events; however, rare events are challenging to study. Any adverse events should be weighed against the protective benefits that vaccines provide.     

Perspectives on the receipt of a COVID-19 vaccine: A survey of employees in two large hospitals in Philadelphia

BackgroundHealth care personnel have been identified by the ACIP as a priority group for COVID-19 vaccination. We conducted a survey in November-December 2020 at two large, academic hospitals in Philadelphia to evaluate the intention of hospital employees to be vaccinated.MethodsThe survey was sent electronically to all employees (clinical and nonclinical staff) at a children’s hospital and an adult hospital. The survey was voluntary and confidential. Questions focused on plans to receive a COVID-19 vaccine when available, reasons why employees would/would not get vaccinated, when employees planned to be vaccinated, vaccine safety and efficacy features that would be acceptable, and past history of receipt of other vaccines by the employee and family. Responses were analyzed using univariate and multiple logistic regression methods.ResultsA total of 12,034 hospital employees completed the survey (a 34.5% response rate). Overall, 63.7% of employees reported that they planned to receive a COVID-19 vaccine, 26.3% were unsure, and 10.0% did not plan to be vaccinated. Over 80% of those unsure or unwilling to be vaccinated expressed concerns about vaccine side effects and the vaccines’ newness. In multivariable logistic regression, persons planning to take a COVID-19 vaccine were more likely to be older, male, more educated, Asian or White, up-to-date on vaccinations, without direct patient contact, and tested for COVID-19 in the past. No significant difference in intention to be vaccinated was found between those with higher versus lower levels of exposure to COVID-19 patients or the number of previous exposures to patients with COVID-19.ConclusionsWhile the majority of hospital employees are planning to receive a COVID-19 vaccine, many are unsure or not planning to do so. Further education of hospital employees about the safety, efficacy, and value of the currently available COVID-19 vaccines is critical to vaccine acceptance in this population.     

COVID-19 vaccine uptake before and after a vaccine mandate at a major academic hospital: Trends by race/ethnicity and level of patient contact

ObjectivesTo assess vaccine coverage rates before and after implementation of a COVID-19 vaccine mandate among Health care Personnel (HCP) and demographic characteristics associated with vaccine uptake Design, Setting, and Participants: Cohort study conducted among 10,889 hospital employees followed from Dec 16, 2020 - October 31, 2021, at a large academic hospital in Philadelphia. Main Outcome and Measures: Time to COVID-19 vaccination and vaccine series completion rates before and after implementation of a COVID-19 vaccine mandate based on age, gender, race/ethnicity, and level of patient contact/occupational group.ResultsThe vaccination series completion rate was 86.0% prior to mandate announcement, and increased to 98.7% after mandate implementation. Rates before mandate announcement were highest among Asians (96.2%), Whites (94.0%), males (89.7%), employees ≥ 65 years of age (95.2%), and employees with direct patient care (physicians, 99.0%, and nurses, 93.3%). Hospital educational initiatives (including Town Halls and discussions with Black and Hispanic employees with the lowest vaccination rates) appeared to improve uptake. The largest increase in series completion after mandate announcement occurred among Blacks, those of other/multiracial backgrounds, and Hispanics (35.6%, 22.4%, and 10.8%, respectively) as well as those with some or no direct patient contact (24.5% and 18.3%, respectively). Medical or religious exemptions were approved for 64 (<0.6%) employees and 38 (<0.4%) left their positions (8 voluntary, 30 involuntary) specifically due to the COVID-19 vaccine mandate. No clinically meaningful differences by age, gender, or race/ethnicity for those who were vaccinated under the mandate versus those who left their positions were noted.Conclusions and RelevanceThese results suggest that while mandates may be challenging to institutions and enforcement unpopular, they play an important role in reducing hesitancy and securing high vaccination rates among HCP, a group at high risk of COVID-19 given their employment and who can be a source of disease transmission to patients.     

Using immersive virtual reality to improve the beliefs and intentions of influenza vaccine avoidant 18-to-49-year-olds: Considerations,effects, and lessons learned

ObjectiveOnly one-third of adults 18–49 years old in the United States receive a recommended annual influenza vaccination. This study examined whether supplementing vaccine information statements (VIS) with an immersive virtual reality (VR), short video or electronic pamphlet story designed to convey the community immunity benefits of influenza vaccination would improve influenza vaccine avoidant participants’ influenza-related perceptions as well as their influenza vaccination-related beliefs, confidence and intentions.MethodA one-way between-subjects experimental design compared the effects of adding a supplemental education experience prior to VIS exposure with flu vaccine avoidant 18-to-49-year-olds. The 171 participants recruited from the community were randomly assigned to one of three modality treatment conditions [VR, video, or e-pamphlet (i.e., story board presented via electronic tablet)] or a VIS-only control condition.ResultsCompared to the modalities, the VR intervention created a stronger perception of presence (i.e., feeling of “being there” in the story), which, in turn, increased participants’ concern about transmitting influenza to others and raised vaccination intention. Increased concern about transmitting influenza to others was associated with positive effects on influenza vaccination-related beliefs, including confidence that one’s flu vaccination would protect others. Neither the e-pamphlet nor the video intervention were able to elicit a sense of presence nor were they able to improve the impact of the VIS on the outcome measures.ConclusionsImmersive VR has much potential to increase understanding of key immunization concepts, such as community immunity, through creative executions that increase a sense of presence. Given the need to increase influenza vaccination uptake among 18-to-49-year-olds, and the projected growth in VR accessibility and use, additional applications and assessments related to vaccination communication and education are needed and warranted. By increasing the ability to convey key vaccine and immunization concepts, immersive VR could help address vaccination hesitancy and acceptance challenges.     

Preparing for introduction of a dengue vaccine: recommendations from the 1st Dengue v2V Asia-Pacific Meeting

Infection with dengue virus is a major public health problem in the Asia-Pacific region and throughout tropical and sub-tropical regions of the world. Vaccination represents a major opportunity to control dengue and several candidate vaccines are in development. Experts in dengue and in vaccine introduction gathered for a two day meeting during which they examined the challenges inherent to the introduction of a dengue vaccine into the national immunisation programmes of countries of the Asia-Pacific. The aim was to develop a series of recommendations to reduce the delay between vaccine licensure and vaccine introduction. Major recommendations arising from the meeting included: ascertaining and publicising the full burden and cost of dengue; changing the perception of dengue in non-endemic countries to help generate global support for dengue vaccination; ensuring high quality active surveillance systems and diagnostics; and identifying sustainable sources of funding, both to support vaccine introduction and to maintain the vaccination programme. The attendees at the meeting were in agreement that with the introduction of an effective vaccine, dengue is a disease that could be controlled, and that in order to ensure a vaccine is introduced as rapidly as possible, there is a need to start preparing now.     

Effect of donor funding for immunization from Gavi and other development assistance channels on vaccine coverage: Evidence from 120 low and middle income recipient countries

Donor assistance for immunization has remained resilient with increased resource mobilization efforts in recent years to achieve current global coverage targets. As a result, more countries continue to introduce new vaccines while optimizing coverage for traditional vaccines. Gavi the Vaccine Alliance has been at the forefront of immunization support specifically among low and middle income countries, alongside other channels of development assistance which continue to play a vital role in immunization.Using available recipient country level data from 1996 to 2016, we estimate the impact of Gavi support for vaccines and health systems strengthening on vaccine coverage for 3 dose DPT, 3 dose pneumococcal conjugate vaccine, 3 dose pentavalent, 2 dose measles and 2 dose rotavirus vaccines. We investigate the same effects of total aid for immunization from other channels of development assistance. Standard time series cross sectional analysis methods are applied to investigate the effects of vaccine support controlling for country income, governance and population, with robustness tests implemented using different model specifications. Double counting was eliminated and results are presented in real 2017 US dollars.We found significant positive effects of aid particularly among the newer vaccines. Using 2016 country specific disbursements and coverage levels as baseline, we estimated that among recipient countries below the universal target, additional DAH per capita required to reach 90%, ranged from 0.01USD to 4.33USD for PCV, 0.03USD to 9.06USD for pentavalent vaccine and 0.01USD to 2.57USD for rotavirus vaccine. The estimated number of children vaccinated through 2016, attributable to Gavi support totaled 46.6million, 75.2million and 12.3million for PCV, pentavalent and rotavirus vaccines respectively.Our analysis suggests substantial success both from a historical and prospective perspective in the implementation of global immunization initiatives thus far. As more vaccines are rolled out and countries transition from donor aid, strategies for fiscal sustainability and efficiency need to be strengthened in order to achieve universal immunization coverage.     

Association between social capital and second dose of measles vaccination in Japan: Results from the A-CHILD study

Background and Objectives

Measles vaccination is important to prevent outbreak, and social capital can be an important preventive factor. However, there have been very few studies that investigated the association between social capital and measles vaccination, especially the second dose, which is more likely to be suboptimal. This study aimed to investigate the association between social capital and second dose of measles vaccine.

Introduction of inactivated poliovirus vaccine in the Philippines: Effect on health care provider and infant caregiver attitudes and practices

BackgroundThe introduction of inactivated poliovirus vaccine (IPV) to the Philippines’ national immunization schedule meant the addition of a third injectable vaccine at a child’s 14-week immunization visit. Although previous studies have shown that providing multiple vaccines at the same time affected neither the risk of severe adverse events nor vaccine efficacy, concerns were raised that providing three injections at a single visit, with two injections in one leg, might be unacceptable to health care providers (HCP) and infant caregivers.MethodsWe conducted pre- and post-IPV introduction surveys on the acceptance and acceptability of the additional injectable vaccine in three of the Philippines’ 17 administrative regions. Regions 3 and 6 were included in the pre-introduction phase and Regions 3, 6 and 10 were included in the post-introduction phase. Thirty public health centers (PHCs) were randomly sampled from each region. HCPs and infant caregivers were interviewed. In addition, vaccination records from a minimum of 20 eligible children pre-introduction and 10 children post-introduction per PHC were reviewed.Results and discussionWe interviewed 89 HCPs and 286 infant caregivers during the pre-introduction phase and 137 HCPs and 455 caregivers during the post-introduction phase. Among 986 vaccination records reviewed post-introduction, 84% (n = 826) of children received all three recommended injections at one visit, with a range from 61% (209/342) in Region 10 to 100% (328/328) in Region 3. The proportion of HCPs reporting that they had administered three or more injectable vaccines and the proportion of caregivers that would be comfortable with their child receiving three or more injectable vaccines at one visit increased from pre- to post-introduction (p < 0.0001 for both). Eighty-seven percent of HCPs that had administered three or more injectable vaccines post-introduction reported being comfortable or very comfortable with the number of vaccines they had administered.     

A cluster randomized trial to determine the effectiveness of a novel,digital pendant and voice reminder platform on increasing infant immunization adherence in rural Udaipur,India

BackgroundFive hundred thousand children under the age of 5 die from vaccine preventable diseases in India every year. More than just improving coverage, increasing timeliness of immunizations is critical to ensuring infant health in the first year of life. Novel, culturally appropriate community engagement strategies are worth exploring to close the immunization gap. In our study, a digital NFC (Near Field Communication) pendant worn on black thread and voice call reminder system was tested for the effectiveness in improving DTP3 adherence within 2 monthly camps from DTP1 administration.MethodA cluster randomized controlled trial was conducted in which 96 village health camps were randomized to 3 arms: NFC sticker, NFC pendant, and NFC pendant with voice call reminder in local dialect. Randomization was done across 5 blocks in the Udaipur District serviced by Seva Mandir from August 2015 to April 2016.ResultsIn terms of our three primary outcomes related to DTP3 adherence, point estimates show conflicting results. Two outcomes presented adherence in the control. DTP3 completion within two camps after DTP1 showed higher adherence in the Control (Sticker) (74.2%) arm compared to the Pendant (67.2%) and Pendant and Voice arms (69.3%). Likewise, the estimate for DTP3 completion within 180 days of birth in the Control (Sticker) (69.4%) arm was higher than estimates in the Pendant (57.4%) and Pendant and Voice arms (58.7%). However, one outcome displayed higher adherence in the intervention. DTP3 completion within two months from the time of registration was higher in the Pendant (37.7%) and Pendant and Voice arms (38.7%) compared to the Control (Sticker) arm (27.4%). In all primary outcomes, differences in adherence were statistically insignificant both before and after controlling for confounding factors. In terms of secondary outcomes, our results suggest that providing a necklace generated significant community discussion (H = 8.8796, df = 2, p = .0118), had strong satisfaction among users (χ2=26.039, df = 4, p < .0001), and resulted in increased visibility within families (grandmothers: χ2=34.023, df = 2, p < .0001, fathers: χ2 = 34.588, df = 2, p < .0001).ConclusionNeither the NFC necklace nor the necklace with additional voice call reminders in the local dialect directly resulted in an increase in infant immunization timeliness through DTP3, the primary outcome. Still our process outcomes suggest that our culturally symbolic necklace has potential to be an assistive tool in immunization campaigns. Follow-on work will seek to examine whether positive behavior change towards vaccines can be fostered with earlier engagement of this platform beginning in the prenatal stage, under a continuum of care framework.     

Evaluating the first introduction of rotavirus vaccine in Thailand: Moving from evidence to policy

BackgroundWe assessed the effectiveness and possible impact of introducing rotavirus vaccine into the routine immunization program.MethodsTwo provinces were selected for an observational study, one where vaccine was introduced and another where vaccine was not available. In these areas, two sub-studies were linked. The prospective cohort study enrolled children 2 month old and followed them to the age of 18 months to detect all diarrhea episodes. The hospital surveillance study enrolled all children up to age 5 hospitalized with diarrhea whose fecal samples were tested for rotavirus. Rates of rotavirus hospitalizations in older children who had not been vaccinated in both settings provided data to determine whether immunization had an indirect herd effect. The key endpoints for the study were both vaccine effectiveness (VE) based upon hospitalized rotavirus diarrhea and herd protection.FindingsFrom the cohort study, the overall VE for hospitalized rotavirus diarrhea was 88% (95%CI 76–94). Data from hospital surveillance indicated that for 2 consecutive years, the seasonal peak of rotavirus admissions was no longer present in the vaccinated area. Herd protection was observed among older children born before the rotavirus vaccine program was introduced, who experienced a 40–69% reduction in admission for rotavirus.ConclusionsRotavirus vaccine was highly effective in preventing diarrheal hospitalizations and in conferring herd protection among older children who had not been vaccinated.     

Post-marketing surveillance of adverse events following immunization with inactivated quadrivalent and trivalent influenza vaccine in health care providers in Western Australia

In 2015, inactivated quadrivalent influenza vaccine (QIV) was first introduced into the Australian market. A routine vaccine safety surveillance system in Western Australia was used to conduct post-licensure surveillance of adverse events following immunization with inactivated QIV and trivalent influenza vaccines (TIV) in a sample of 1685 healthcare providers (HCPs). A similar percentage of HCPs who received QIV reported having any reaction seven days post-vaccination as HCPs who received TIV (13.6 vs. 12.8%, respectively; p = 0.66). However, a slightly higher percentage of HCPs who received QIV reported pain or swelling at the injection site as compared to HCPs who received TIV (6.9% vs. 4.2%, respectively; p = 0.02). No serious vaccine-associated adverse events were detected during follow-up of either vaccine. Acknowledging the study limitations, the results of this post-marketing surveillance support the safety of QIV, suggesting there is little difference in the reactogenicity of QIV as compared to TIV.     

Non-specific effects of rabies vaccine on the incidence of self-reported common infectious disease episodes: A randomized controlled trial

Vaccines may affect recipients’ immune systems in ways that change morbidity or mortality rates to unrelated infections in vaccinated populations. It has been proposed that these non-specific effects differ by type of vaccine and by sex, with non-live vaccines enhancing susceptibility of females to unrelated infections, and live vaccines enhancing resistance in both sexes. Rabies vaccine–a non-live vaccine–has been associated with protection against unrelated central nervous system infections. Data from randomized controlled trials are needed to assess this effect against other illnesses. This phase IV, single-site, participant-blinded, randomized, placebo-controlled trial in a population of veterinary students on the rabies-free island of St. Kitts assessed the effect of a primary course of rabies vaccine on the incidence rate of weekly self-reported new episodes of common infectious disease (CID) syndromes, defined as a new episode of any one of the following syndromes in a particular week: upper respiratory illness (URI), influenza-like illness (ILI), diarrheal illness (DIA) or undifferentiated febrile illness (UFI). As a secondary objective, we tested for modification of the effect of rabies vaccine on study outcomes by sex. 546 participants were randomized (274 to rabies vaccine and 272 to placebo). No statistically significant differences between groups were observed for any study outcomes: CID incidence rate ratio (IRR) 0.95 (95% CI 0.77–1.18); URI IRR 1.15 (95% CI 0.86–1.54); ILI IRR 0.83 (95% CI 0.54–1.27); DIA IRR 0.93 (95% CI 0.70–1.24) and UFI IRR 1.09 (95% CI 0.48–2.44). In a secondary analysis, there was little evidence that sex modified the effect of vaccination on any of the evaluated outcomes, although the power to detect this was low. In conclusion, rabies vaccine did not provide protection against mild self-reported illness among a young and healthy group of adults attending veterinary school.Clinical trial registration. ClinicalTrials.gov: NCT03656198.