Adverse events following influenza immunization: understanding the role of age and sex interactions

Enhanced passive safety surveillance of standard-dose and high-dose influenza vaccines in Finland and Germany 2023-24 season

Enhanced Passive Safety Surveillance was used to detect safety signals before the peak period of immunization with quadrivalent inactivated influenza vaccines (IIV4) in Finland (standard dose [SD]) and Germany (high dose [HD]) in the 2023-24 season. The primary objective was to evaluate adverse drug reactions (ADRs) occurring ≤7 days following IIV4 vaccination. Enrolled participants were vaccinated in routine clinical care settings and encouraged to report ADRs. Exposure data and ADR reports were collected in a near real-time manner using an electronic system. Vaccinee reporting rate (RR) with 95% confidence interval (CI) was calculated as the number of vaccinees reporting ≥ 1 ADR divided by total number of vaccinees. In Finland for SD-IIV4, among 1,003 vaccinees aged ≥ 6 months, 81 reported a total of 192 suspected ADRs occurring ≤ 7 days following vaccination (vaccinee RR 8.08%; 95% CI 6.46, 9.94). In Germany for HD-IIV4, among 1,075 vaccinees aged ≥ 60 years, 15 reported 46 ADRs that occurred in ≤ 7 days of vaccination (vaccinee RR 1.40%; 95% CI 0.78, 2.29). No safety signal was detected during this surveillance. The 2023-24 season surveillance did not suggest any clinically significant changes in safety profile compared with previously reported safety data for SD-IIV4 and HD-IIV4.

Circadian Variation in the Response to Vaccination: A Systematic Review and Evidence Appraisal

Molecular timing mechanisms known as circadian clocks drive endogenous 24-h rhythmicity in most physiological functions, including innate and adaptive immunity. Consequently, the response to immune challenge such as vaccination might depend on the time of day of exposure. This study assessed whether the time of day of vaccination (TODV) is associated with the subsequent immune and clinical response by conducting a systematic review of previous studies. The Cochrane Library, PubMed, Google, Medline, and Embase were searched for studies that reported TODV and immune and clinical outcomes, yielding 3114 studies, 23 of which met the inclusion criteria. The global severe acute respiratory syndrome coronavirus 2 vaccination program facilitated investigation of TODV and almost half of the studies included reported data collected during the COVID-19 pandemic. There was considerable heterogeneity in the demography of participants and type of vaccine, and most studies were biased by failure to account for immune status prior to vaccination, self-selection of vaccination time, or confounding factors such as sleep, chronotype, and shiftwork. The optimum TODV was concluded to be afternoon (5 studies), morning (5 studies), morning and afternoon (1 study), midday (1 study), and morning or late afternoon (1 study), with the remaining 10 studies reporting no effect. Further research is required to understand the relationship between TODV and subsequent immune outcome and whether any clinical benefit outweighs the potential effect of this intervention on vaccine uptake.

SARS-CoV-2 mucosal vaccine protects against clinical disease with sex bias in efficacy

Intranasal mucosal vaccines can more effectively induce mucosal immune responses against SARS-CoV-2. Here, we show in hamsters that an intranasal subunit mucosal vaccine boost with the beta variant S1 can prevent weight loss, in addition to reducing viral load, which cannot be studied in macaques that don't develop COVID-like disease. Protective efficacy against both viral load and weight loss correlated with serum antibody titers. A sex bias was detected in that immune responses and protection against viral load were greater in females than males. We also found that priming with S1 from the Wuhan strain elicited lower humoral immune responses against beta variant and led to less protection against beta viral challenge, suggesting the importance of matched antigens. The greater efficacy of mucosal vaccines in the upper respiratory tract and the need to consider sex differences in vaccine protection are important in the development of future improved COVID-19 vaccines.

Sex differences in adverse events following seasonal influenza vaccines: a meta-analysis of randomised controlled trials

BACKGROUND

Despite being a vaccine-preventable disease, influenza remains a major public health threat with vaccine safety concerns reducing vaccine acceptability. Immune responses to vaccines and adverse events may differ between males and females, but most studies do not report results by sex. Using data from clinical trials, we explored sex differences in adverse events following seasonal influenza vaccines.

METHODS

We obtained data for phase III randomised controlled trials identified through a systematic review and clinical trials registries, and performed a two-stage meta-analysis. Risk ratios (RR) and 95% confidence intervals (95% CI) comparing solicited reactions in females versus males were pooled using the Mantel-Haenszel method and a random-effects model. We used the ROBINS-I tool to assess risk of bias and the I2 statistic for heterogeneity. Main analysis was stratified by age: 18-64 years and ≥65 years.

RESULTS

The dataset for this analysis included 34 343 adults from 18 studies (12 with individual-level data and 6 with aggregate data). There was a higher risk of injection site reactions in females compared with males for both younger and older participants, with RRs of 1.29 (95% CI 1.21 to 1.37) and 1.43 (95% CI 1.28 to 1.60), respectively. Higher risk in females was also observed for systemic reactions, with RRs of 1.25 (95% CI 1.20 to 1.31) and 1.27 (95% CI 1.20 to 1.34) for younger and older participants, respectively. We also observed elevated risks of severe reactions in females, with a higher RR in younger versus older participants for systemic reactions (RRs 2.12 and 1.48, p=0.03, I2=79.7%). RRs were not found to vary between quadrivalent and trivalent vaccines.

CONCLUSION

This meta-analysis suggested a higher risk of solicited reactions following influenza vaccines for females compared with males, irrespective of age and vaccine type. Transparent communication of this risk could increase the trust in vaccines and limit vaccine hesitancy. Future studies should report results stratified by sex and explore the role of gender in the occurrence of adverse events.

The Effect of Sex on the Incidence, Latency, Duration and Perceived Burden of Adverse Events Following Seasonal Influenza Vaccination in the Netherlands

INTRODUCTION

The annual reformulation of the seasonal influenza vaccine results in fluctuating frequencies and severity of adverse effects following immunization (AEFIs), which stresses the importance of pharmacovigilance. Also, sex-related factors are known to influence the development of AEFIs. This study aims to describe the difference in incidence and course (i.e., time-to-onset, time-to-recovery, and perceived burden) of AEFIs between males and females after seasonal influenza vaccination.

METHODS

We assessed data from cohort event monitoring studies, which were performed over nine consecutive years (2013-2021), each covering several months during the seasonal influenza campaign in the Netherlands. Participants reported information about AEFIs over a 30-day period in three questionnaires. The effect of sex, age, body mass index, study year, and comorbidities on the incidence of any AEFI, local reactions, fever and the five most reported AEFIs was analyzed using logistic regression. The difference in time-to-onset, time-to-recovery, and perceived burden between males and females was analyzed by the Kruskal-Wallis test.

RESULTS

The cohort included 7789 participants (53.0% females). Females had around 2.5-fold (p < 0.001) higher odds of developing any AEFI compared with males. Some study years and comorbidities were positively associated with AEFI incidence, whereas age was negatively associated. An AEFI had a significant shorter time-to-onset, a longer time-to-recovery, and a higher perceived burden in females compared to males.

CONCLUSION

Overall, the results confirm that females experience AEFIs more often than males. Additionally, this study shows that the course of AEFIs only partially differs between the sexes.

Efficacy and feasibility of SMS m-Health for the detection of adverse events following immunisation (AEFIs) in resource-limited setting-The Zimbabwe stimulated telephone assisted rapid safety surveillance (Zm-STARSS) randomised control trial

INTRODUCTION

The mHealth active participant centred (MAPC) adverse events following immunisation (AEFI) surveillance is a promising area for early AEFI detection resulting in risk minimisation. Passive (spontaneous) AEFI surveillance is the backbone for vaccine pharmacovigilance, but has inherent drawbacks of under reporting, and requires strengthening with active surveillance methods.

AIM

The Zimbabwe stimulated telephone assisted rapid safety surveillance (Zm-STARSS) randomised controlled trial (RCT) sought to evaluate the efficacy and feasibility of AEFI detection using a short message service (SMS) and computer assisted telephone interview (CATI) approach.

METHOD

A multicentre Zm-STARSS RCT enrolled consented adult vaccinees or parents or guardians of children receiving vaccines, including COVID-19 vaccines, at study vaccination clinics. At enrolment study participants were randomised to either SMS-CATI group or control group. SMS prompts were sent on days 0-2 and 14 post-vaccination to SMS-CATI group to ascertain if a medically attendance or attention due to an Adverse event following immunisation (AEFI) had occurred. However, no SMSs were sent to the control group. SMS-CATI group who responded "Yes" to SMS prompts were interviewed by research healthcare workers (RHCWs) who completed a CATI to determine if an AEFI had occurred whilst an AEFI in control group was determined from passive AEFI reporting channels. The primary study outcome was the AEFI detection rate in the SMS-CATI group compared to the control group.

RESULTS

A total of 4560 participants were enrolled after signed informed consent, all were encouraged to report AEFIs and randomised automatically on 1:1 basis into two arms SMS CATI intervention group (n = 2280) and a control passive AEFI surveillance group (n = 2280) on day 0. A total of 704 (31 %) participants responded to the SMS prompts, with 75 % (528/704) indicating "No" and 25 % (176/704) reporting "Yes" to seeking medical attention or attendance post-immunisation. 69 % (121/176) completed a CATI survey but in only 36 % (44/121) was the AEFI confirmed. There were no AEFIs reported in control group participants. The detection rate of a AEFI associated with medically attendance or attention using the SMS-CATI methodology was 2 % (44/2280) on an intention to treat cohort.

CONCLUSION

Despite the low SMS response and CATI completion rate, we demonstrated that Zm-STARSS SMS system improves AEFI detection compared to passive AEFI surveillance. We recommend that this and similar approaches are explored further using cost-effective multi-channel digital approaches for holistic pharmacovigilance to improve AEFI detection in Low Middle-Income Countries (LMICs) for all vaccines.

Association of post-vaccination adverse reactions after influenza vaccine with mortality and cardiopulmonary outcomes in patients with high-risk cardiovascular disease: the INVESTED trial

AIMS

Influenza vaccination is associated with reduced cardiopulmonary morbidity and mortality among patients with heart failure or recent myocardial infarction. The immune response to vaccination frequently results in mild adverse reactions (AR), which leads to vaccine hesitancy. This post hoc analysis explored the association between vaccine-related AR and morbidity and mortality in patients with high-risk cardiovascular disease.

METHODS AND RESULTS

The INVESTED trial randomized 5260 patients with recent heart failure hospitalization or acute myocardial infarction to high-dose trivalent or standard-dose quadrivalent inactivated influenza vaccine. We examined the association between vaccine-related AR and adverse clinical outcomes across both treatment groups in propensity-adjusted models. Among 5210 participants with available information on post-vaccination symptoms, 1968 participants (37.8%) experienced a vaccine-related AR. Compared to those without AR, post-vaccination AR, most commonly injection site pain (60.3%), were associated with lower risk for the composite of all-cause death or cardiopulmonary hospitalization (hazard ratio [HR] 0.83, 95% confidence interval [CI] 0.75-0.92, p < 0.001), cardiopulmonary hospitalizations (HR 0.85 [95% CI 0.76-0.95], p = 0.003), all-cause death (HR 0.77 [95% CI 0.62-0.96], p = 0.02), cardiovascular hospitalizations (HR 0.88 [95% CI 0.78-0.99], p = 0.03) and non-cardiopulmonary hospitalizations (HR 0.80 [95% CI 0.69-0.92], p = 0.003). While mild (76.4%) and moderate (20.6%) AR were most common and together associated with lower risk for the primary outcome (HR 0.81 [95% CI 0.74-0.90], p < 0.001), severe AR (2.9%) were related to increased risk (HR 1.68 [95% CI 1.17-2.42], p = 0.005).

CONCLUSION

Mild to moderate post-vaccination reactions after influenza vaccine were associated with reduced risk of cardiopulmonary hospitalizations and all-cause mortality in patients with high-risk cardiovascular disease, while severe reactions may indicate increased risk. Mild to moderate AR to influenza vaccination may be a marker of immune response and should not deter future vaccinations.

Health behaviors are largely not predictive of adverse events following influenza vaccination

BACKGROUND

Identifying health behaviors associated with adverse events following immunization (AEFI) could identify intervention targets for AEFI prevention.

METHODS

University employees receiving an influenza vaccination (n = 1301) completed a series of online surveys for health behaviors including sleep, exercise, dietary intake, and smoking habits, and emotional state (baseline), and for indications of AEFI (three days post-vaccination) and influenza-like illness (ILI) symptoms (fortnightly follow-up for 4 months).

RESULTS

29.9% of participants reported an AEFI and 46.0% reported experiencing ILI during follow-up. Multivariate logistic regression revealed usual sleep duration was associated with AEFI (odds ratio 1.20, 95% confidence interval 1.03-1.41), increasing with each hour of sleep. ILI was associated with reporting AEFI (1.70, 1.24-2.33), increasing BMI (1.03, 1.00-1.06) and survey response frequency (1.13, 1.04-1.22), and decreased with better usual sleep quality (0.96, 0.92-1.00) and with increasing age (0.98, 0.96-1.00). Sex stratification revealed no significant predictors of AEFI for either sex; in women, experiencing AEFI increased likelihood of ILI (1.88, 1.25-2.85) and in men, survey completion frequency increased ILI likelihood (1.19, 1.05-1.36).

CONCLUSIONS

Our study suggests modifying health behaviors would not alter AEFI risk and reactogenicity may signal weaker immunogenicity but confirmation through objective measures is warranted.