Really just a little prick? A meta-analysis on adverse events in placebo control groups of seasonal influenza vaccination RCTs

Moderators of nocebo effects in controlled experiments: A multi-level meta-analysis

Nocebo effects are a heterogenous phenomenon in which contextual cues trigger or exacerbate symptoms independently of active interventions. Suggestion, conditioning, and social observation are widely recognised as hallmark methods for inducing nocebo effects, but the extent to which nocebo effects are differentially influenced by suggestion type (e.g., direct or indirect suggestion) and mode of administration (e.g., verbal, textual, visual, etc.) across symptom domains remains unknown. We conducted a pre-registered meta-analysis (PROSPERO registration number CRD42023402097) to quantitatively synthesize available research on the factors that moderate effects in controlled nocebo experiments. Of 8469 search results, 105 experiments comprising 5017 participants and 391 effect sizes were analyzed. A multi-level meta-analysis revealed an overall moderate effect size for nocebo effects, g=0.50, [0.39, 0.62]. The magnitude of symptom expectancy effects was a significant moderator of nocebo effects. Verbal suggestion and social observation yielded moderate and comparable nocebo effects whereas technological devices, sham stimulation, and conditioning were independently associated with the induction of large nocebo effects. Greater specificity in the reporting of nocebo induction methods is required to elucidate the efficacy of different types of suggestions in inducing nocebo effects.

Adverse Events Following Vaccines: From Detection to Research Translation

Vaccines are lifesaving interventions that reduce the morbidity and mortality of disease. Fortunately, serious adverse events with vaccination are uncommon, but they must promptly be recognized and evaluated to assess and clarify the safety of future administration, a process that the public must understand in order to feel safe in receiving vaccines. In this article, we provide a review of vaccine development, discuss the process by which safety is ensured, and describe key adverse events associated with their administration. We review in detail existing mechanisms for reporting these events and assessing them following recovery, as well as communication related to vaccine safety. We also describe barriers to vaccination, such as nocebo effects and antivaccination groups, and use lessons learned from the successful development of COVID-19 vaccines during the recent pandemic to define future opportunities and directions for vaccine safety.

Vaccine safety in children with genetically confirmed mitochondrial disease

We here explore adverse events following immunization (AEFI) in children with mitochondrial disease (MD) recruited from two expertise centers in Austria (SALK) and The Netherlands (RUMC). Parents completed a questionnaire on the type of immunizations received and AEFI in a post-vaccination exposure period of seven days. 95 individuals were invited to this study, of whom 30 (median age 13.4 years) participated. Together these individuals had received 376 immunizations with a median of 12 vaccinations each. In 316 of 376 (84 %) vaccinations no AEFI occurred, 22 patients (73 %) never experienced any AEFI. Eight patients experienced 76 AEFI after 60 vaccinations, these were mild (redness (n = 9) /pain at injection site (n = 21), fever (n = 44), gastrointestinal complaints (n = 2)). None had a metabolic deterioration or seizures, no patient was admitted to the hospital. Although our data is limited by the small sample size, this may aid in discussing responsible immunization decisions with parents.

Trait responsiveness to verbal suggestions predicts nocebo responding: A meta-analysis

BACKGROUND

Nocebo responding involves the experience of adverse health outcomes in response to contextual cues. These deleterious responses impact numerous features of mental and physical health but are characterized by pronounced heterogeneity. Suggestion is widely recognized as a contributing factor to nocebo responding but the moderating role of trait responsiveness to verbal suggestions (suggestibility) in nocebo responding remains poorly understood.

OBJECTIVE

We conducted a pre-registered meta-analysis (PROSPERO registration number CRD42023425605) to quantitatively synthesize available research on the relationship between suggestibility and nocebo responding.

METHODS

Four electronic databases were searched for original studies involving both the assessment of suggestibility and symptom reports in response to an inactive stimulus.

RESULTS

Of 7729 search results, 10 articles presenting 13 correlations between suggestibility and nocebo responding were analysed. A random-effects meta-analysis revealed a significant, albeit weak, positive correlation, r = .21 [95% CI: .04, .37], between suggestibility and nocebo responses, such that more highly suggestible individuals displayed larger responses. Sensitivity and meta-regression analyses demonstrated that studies of higher methodological quality, including those that maintained experimenter blinding, exhibited stronger effect sizes.

CONCLUSION

These results corroborate proposals that trait responsiveness to verbal suggestions confers greater response to nocebos and warrants renewed attention to the role of suggestibility in symptom induction and perception.

Does health anxiety and vaccine concern predict self-reported adverse events following COVID-19 vaccination?-A Danish national cohort study

OBJECTIVES

The nocebo effect refers to an expectation of sickness that leads to sickness in the expectant. Studies have found COVID-19 vaccines to be associated with the nocebo effect. However, the literature in this field is sparse yet important with the continuation of booster vaccines.

STUDY DESIGN

National cohort study.

METHODS

This study used data from the Danish national cohort "BiCoVac", which contains self-reported information on both health anxiety and specific COVID-19 vaccine concern, as well as 19 systemic AEs following COVID-19 vaccination. Simple and multiple logistic regression was used to estimate the association between health anxiety and specific COVID-19 vaccine concern with having one or more systemic AEs following COVID-19 vaccination. Inverse probability weights were used to compensate for the initial dropout and loss to follow-up.

RESULTS

Of the 85,080 participants in the study, 4 % reported health anxiety, 30 % reported specific COVID-19 vaccine concern, and 26 % one or more systemic AEs following vaccination. After adjusting for covariates, participants with health anxiety had higher odds of reporting one or more systemic AEs following vaccination compared to those without (OR, 1·21 CI 95 % [1·10; 1·33]). For specific COVID-19 vaccine concern, the OR was 1·51 CI 95 % [1·45; 1·58].

CONCLUSIONS

Participants with specific COVID-19 vaccine concern had higher odds of reporting one or more systemic AEs following vaccination compared with those who had no specific COVID-19 vaccine concern. There might be a potential to reduce AEs, with positive framing of AEs and information about nocebo. Reporting of AEs was also associated with health anxiety, but to a lesser degree.

Can side effect expectations be assessed implicitly? A comparison of explicit and implicit expectations of vaccination side effects

OBJECTIVE

Treatment expectations alter the probability of experiencing unpleasant side effects from an intervention, including vaccinations. To date, expectations have mostly been assessed explicitly bearing the risk of bias. This study aims to compare implicit expectations of side effects from COVID-19 and flu vaccinations and to examine their relationships with vaccine attitudes and intentions.

METHODS

N = 248 participants took part in a cross-sectional online survey assessing explicit and implicit expectations, as well as vaccine-related attitudes and personal characteristics. A Single Category Implicit Association Test (SC-IAT) was developed to assess implicit side effect expectations. Explicit side effect expectations were measured with the Treatment Expectation Questionnaire (TEX-Q).

RESULTS

Whereas explicit and implicit expectations regarding COVID-19 vaccine were significantly correlated (r = -0.325, p < .001), those correlations could not be found regarding flu vaccine (r = -0.072, p = .32). Explicit measures (COVID-19: β = -0.576, p < .001; flu: β = -0.301, p < .001) predicted the intention to receive further vaccinations more than implicit measures (COVID-19: β = -0.005, p = .93; flu: β = 0.004, p = .96). Explicit measures (COVID-19: OR = 0.360, p < .001; flu: OR = 0.819, p = .03) predicted vaccination status, while implicit measures did not (COVID- 19: OR = 2.643, p = .35; flu: OR = 0.829, p = .61).

CONCLUSION

Expectations to experience side effects from vaccinations can be measured implicitly, in addition to explicit measures. Further investigation needs to determine the relative contribution and additive value of using implicit measures to assess treatment expectations.

Risk of stroke within 3, 7, 14, 21 and 30 days after influenza vaccination in Alberta, Canada: A population-based study

BACKGROUND AND PURPOSE

Influenza vaccination is associated with a longer-term protective effect against stroke; however, it has a short-term inflammatory response which may increase short-term risk of stroke. The aim was to investigate the association between influenza vaccination and short-term risk of stroke in adults.

METHODS

Administrative data were obtained from the Alberta Health Care Insurance Plan for all adults in Alberta, Canada, from September 2009 to December 2018. The hazard of any stroke (acute ischaemic stroke, intracerebral haemorrhage, subarachnoid haemorrhage and transient ischaemic attack) within 3, 7, 14, 21 and 30 days of influenza vaccination compared to unexposed time was analysed using Andersen-Gill Cox models, with adjustment for age, sex, anticoagulant use, atrial fibrillation, chronic obstructive pulmonary disease, diabetes, hypertension, income quintile, and rural or urban home location.

RESULTS

In the entire cohort consisting of 4,141,209 adults (29,687,899 person-years), 1,769,565 (42.7%) individuals received at least one vaccination. In total 38,126 stroke events were recorded with 1309 occurring within 30 days of a vaccination event. Influenza vaccination was associated with a significantly reduced hazard of stroke within 3 days (hazard ratio [HR] 0.83, 95% confidence interval [CI] 0.73-0.93), 7 days (HR 0.87, 95% CI 0.80-0.95), 14 days (HR 0.87, 95% CI 0.81-0.93), 21 days (HR 0.85, 95% CI 0.80-0.91) and 30 days (HR 0.66, 95% CI 0.65-0.68).

CONCLUSIONS

An increased early risk associated with vaccination was not observed. The risk of stroke was reduced at all time points within 30 days after influenza vaccination.

Distinguishing Immunologic and Behavioral Effects of Vaccination

The interpretation of vaccine efficacy estimands is subtle, even in randomized trials designed to quantify the immunologic effects of vaccination. In this article, we introduce terminology to distinguish between different vaccine efficacy estimands and clarify their interpretations. This allows us to explicitly consider the immunologic and behavioral effects of vaccination, and establish that policy-relevant estimands can differ substantially from those commonly reported in vaccine trials. We further show that a conventional vaccine trial allows the identification and estimation of different vaccine estimands under plausible conditions if one additional post-treatment variable is measured. Specifically, we utilize a "belief variable" that indicates the treatment an individual believed they had received. The belief variable is similar to "blinding assessment" variables that are occasionally collected in placebo-controlled trials in other fields. We illustrate the relations between the different estimands, and their practical relevance, in numerical examples based on an influenza vaccine trial.

Patient-reported reactogenicity and safety of COVID-19 vaccinations vs. comparator vaccinations: a comparative observational cohort study

BACKGROUND

In the course of the SARS-CoV-2 pandemic, multiple vaccines were developed. Little was known about reactogenicity and safety in comparison to established vaccines, e.g. influenza, pneumococcus, or herpes zoster. Therefore, the present study aimed to compare self-reported side effects in persons vaccinated against SARS-CoV-2 with the incidence of side effects in persons receiving one of the established vaccines.

METHODS

A longitudinal observational study was conducted over a total of 124 days using web-based surveys. Persons receiving either a vaccination against SARS-CoV-2 or one of the established vaccines (comparator group) were included. In the first questionnaire (short-term survey), 2 weeks after vaccination, mainly local and systemic complaints were evaluated. The long-term survey (42 days after vaccination) and follow-up survey (124 weeks after vaccination) focused on medical consultations for any reason. Multivariate analyses were conducted to determine the influence of the vaccine type (SARS-CoV-2 vs. comparator) and demographic factors.

RESULTS

In total, data from 16,636 participants were included. Self-reported reactogenicity was lowest in the comparator group (53.2%) and highest in the ChAdOx1 group (85.3%). Local reactions were reported most frequently after mRNA-1273 (73.9%) and systemic reactions mainly after vector-based vaccines (79.8%). Almost all SARS-CoV-2 vaccines showed increased odds of reporting local or systemic reactions. Approximately equal proportions of participants reported medical consultations. None in the comparator group suspected a link to vaccination, while this was true for just over one in 10 in the mRNA-1273 group. The multivariate analysis showed that people with SARS-CoV-2 vaccination were not more likely to report medical consultations; patients who had received a regimen with at least one ChAdOx1 were even less likely to report medical consultations. Younger age, female gender and higher comorbidity were mostly associated with higher odds of medical consultations.

CONCLUSION

The rate of adverse reactions after established vaccinations was roughly comparable to previous studies. Two weeks after vaccination, participants in the SARS-CoV-2 vaccination group reported more local and systemic local reactions than participants in the comparator group. In the further course, however, there were no higher odds of medical consultations in either of the two groups. Thus, altogether, we assume comparable safety.

TRIAL REGISTRATION

DRKS-ID DRKS00025881 and DRKS-ID DRKS00025373.

The intersection of biological sex and gender in adverse events following seasonal influenza vaccination in older adults

BACKGROUND

Women/females report more adverse events (AE) following immunization than men/males for many vaccines, including the influenza and COVID-19 vaccines. This discrepancy is often dismissed as a reporting bias, yet the relative contributions of biological sex and gender are poorly understood. We investigated the roles of sex and gender in the rate of AE following administration of the high-dose seasonal influenza vaccine to older adults (≥ 75 years) using an AE questionnaire administered 5-8 days post-vaccination. Participant sex (male or female) was determined by self-report and a gender score questionnaire was used to assign participants to one of four gender categories (feminine, masculine, androgynous, or undifferentiated). Sex steroid hormones and inflammatory cytokines were measured in plasma samples collected prior to vaccination to generate hypotheses as to the biological mechanism underpinning the AE reported.

RESULTS

A total of 423 vaccines were administered to 173 participants over four influenza seasons (2019-22) and gender data were available for 339 of these vaccinations (2020-22). At least one AE was reported following 105 vaccinations (25%), by 23 males and 82 females. The majority of AE occurred at the site of injection, were mild, and transient. The odds of experiencing an AE were 3-fold greater in females than males and decreased with age to a greater extent in females than males. The effects of gender, however, were not statistically significant, supporting a central role of biological sex in the occurrence of AE. In males, estradiol was significantly associated with IL-6 and with the probability of experiencing an AE. Both associations were absent in females, suggesting a sex-specific effect of estradiol on the occurrence of AE that supports the finding of a biological sex difference.

CONCLUSIONS

These data support a larger role for biological sex than for gender in the occurrence of AE following influenza vaccination in older adults and provide an initial investigation of hormonal mechanisms that may mediate this sex difference. This study highlights the complexities of measuring gender and the importance of assessing AE separately for males and females to better understand how vaccination strategies can be tailored to different subsets of the population.

Identifying and Managing Those at Risk for Vaccine-Related Allergy and Anaphylaxis

Immediate hypersensitivity reactions to vaccines, the most severe of which is anaphylaxis, are uncommon events occurring in fewer than 1 in a million doses administered. These reactions are infrequently immunoglobulin E-mediated. Because they are unlikely to recur, a reaction to a single dose of a vaccine is rarely a contraindication to redosing. This narrative review article contextualizes the recent knowledge we have gained from the coronavirus 2019 (COVID-19) pandemic rollout of the new mRNA platform with the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccines within the much broader context of what is known about immediate reactions to other vaccinations of routine and global importance. We focus on what is known about evidence-based approaches to diagnosis and management and what is new in our understanding of mechanisms of immediate vaccine reactions. Specifically, we review the epidemiology of immediate hypersensitivity vaccine reactions, differential diagnosis for immune-mediated and nonimmune reaction clinical phenotypes, including how to recognize immunization stress-related responses. In addition, we highlight what is known about mechanisms and review the rare but important contribution of excipient allergies and specifically when to consider testing for them as well as other key features that contribute to safe evaluation and management.