Do Side Effects to the Primary COVID-19 Vaccine Reduce Intentions for a COVID-19 Vaccine Booster?

Factors associated with the COVID-19 booster vaccine intentions of young adults in the United States

Young adults experience high coronavirus disease 2019 (COVID-19) incidence yet have the lowest vaccination and booster rates among adults. Understanding the factors influencing their intentions regarding boosters is essential for crafting effective public health strategies. We examined the psychosocial factors (attitudes, norms, perceived behavioral control) associated with their intentions to receive a COVID-19 booster. This cross-sectional study included 292 young adults aged 18-25 residing in Philadelphia who completed an online survey from September 2021 and February 2022 (mean age 21.98, standard deviation 2.25; 51% racial/ethnic minorities). The survey included measures of attitudes, norms, and perceived behavioral control related to COVID-19 vaccination. We employed structural equation modeling analysis to examine the intention of young adults to receive the COVID-19 booster and their vaccine-related attitudes, norms, and perceived behavioral control. Covariates included race/ethnicity and gender. Subjective norms were significantly associated with the intention to receive a COVID-19 booster (standardized β̂ = 0.685, p = .018). Attitudes and perceived behavioral control showed no significant association with intention. Subgroup analyses based on race/ethnicity revealed that attitudes (standardized β̂ = 0.488, p = .004) and subjective norms (standardized β̂ = 0.451, p = .050) were predictors among young adults from racial and ethnic minority backgrounds, while only subjective norms (standardized β̂ = 1.104, p = .002) were significant for non-Hispanic White young adults. Public health efforts should prioritize engaging healthcare providers and peer groups in order to influence subjective norms and promote collective responsibility and acceptance for vaccination. Tailored interventions and diverse communication strategies targeting specific subgroups of young adults may be useful to ensure comprehensive and effective vaccination initiatives.

Change in intention and hesitancy regarding COVID-19 vaccines in a cohort of adults in Quebec during the pandemic

Although COVID-19 vaccine uptake was high in Quebec for the primary series, vaccine acceptance decreased for the subsequent booster doses. This article presents the evolution of vaccine intention, self-reported vaccination behaviors, and vaccine hesitancy over 2 years. A series of cross-sectional surveys were conducted in Quebec between March 2020 and March 2023, with a representative sample of 3,330 adults recruited biweekly via a Web panel. Panelists could have answered multiple times over the course of the project. A cohort of respondents was created to assess how attitudes and behaviors about COVID-19 vaccines evolved. Descriptive statistics and multivariate logistic regressions were performed. Among the 1,914 individuals with no or low intention of getting vaccinated in Fall 2021 (Period 1), 1,476 (77%) reported having received at least two doses in the Winter 2023 (Period 2). Not believing in conspiracy theory (OR = 2.08, 95% CI: 1.65-2.64), being worried about catching COVID-19 (OR = 2.12, 95% CI: 1.65-2.73) and not living in a rural area (ORs of other areas are 2.27, 95% CI: 1.58-3.28; 1.66, 95% CI: 1.23-2.26; 1.82 95% CI: 1.23-2.73) were the three main factors associated with being vaccinated at Period 2. Among the 11,117 individuals not hesitant at Period 1, 1,335 (12%) became hesitant at Period 2. The three main factors significantly associated with becoming vaccine hesitant were the adherence to conspiracy theories (OR = 2.28, 95% CI: 1.95-2.66), being a female (OR = 1.67, 95% CI: 1.48-1.90) and being younger than 65 years old (the ORs for 18-34, 35-49, and 50-64 compared with 65 and over are 2.82, 95% CI: 2.32-3.44; 2.39, 95% CI: 2.00-2.86 and 1.82, 95% CI: 1.55-2.15 respectively). As the pandemic is over, monitoring the evolution of vaccine attitudes and uptake will be important.

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.

The Nocebo Effect

Adverse nocebo responses can cause harm to patients and interfere with treatment adherence and effects in both clinic practice and clinical trials. Nocebo responses refer to negative outcomes to active medical treatments in clinical trials or practice that cannot be explained by the treatment's pharmacologic effects. Negative expectancies and nocebo effects are less known than placebo responses. Nocebo effects can be triggered by verbal suggestions, prior negative experiences, observation of others experiencing negative outcomes, and other contextual and environmental factors. As research advances over the years, mechanistic knowledge is accumulating on the neurobiological mechanisms of nocebo effects. This review summarizes studies on different facets of nocebo effects and responses and discusses clinical implications, ethical considerations, and future directions.

Expectations and Prior Experiences Associated With Adverse Effects of COVID-19 Vaccination

Importance

Uptake of vaccination against COVID-19 is strongly affected by concerns about adverse effects. Research on nocebo effects suggests that these concerns can amplify symptom burden.

Objective

To investigate whether positive and negative expectations prior to COVID-19 vaccination are associated with systemic adverse effects.

Design, Setting, and Participants

This prospective cohort study analyzed the association of expected benefits and risks of vaccination, adverse effects at first vaccination, and observed adverse effects in close contacts with severity of systemic adverse effects among adults receiving a second dose of messenger RNA (mRNA)-based vaccines between August 16 and 28, 2021. A total of 7771 individuals receiving the second dose at a state vaccination center in Hamburg, Germany, were invited to participate; of these, 5370 did not respond, 535 provided incomplete information, and 188 were excluded retrospectively. The mobile application m-Path was used for data collection.

Main Outcomes and Measures

Primary outcome was a composite severity index of systemic adverse effects in 12 symptom areas measured once daily with an electronic symptom diary over 7 consecutive days. Data were analyzed by mixed-effects multivariable ordered logistic regression adjusted for prevaccine symptom levels and observation times.

Results

A total of 10 447 observations from 1678 individuals receiving vaccinations (BNT162b2 [Pfizer BioNTech] in 1297 [77.3%] and mRNA-1273 [Moderna] in 381 [22.7%]) were collected. The participants' median age was 34 (IQR, 27-44) years, and 862 (51.4%) were women. The risk for more severe adverse effects was higher for persons expecting a lower benefit of vaccination (odds ratio [OR] for higher expectations, 0.72 [95% CI, 0.63-0.83]; P < .001), expecting higher adverse effects of vaccination (OR, 1.39 [95% CI, 1.23-1.58]; P < .001), having experienced higher symptom burden at the first vaccination (OR, 1.60 [95% CI, 1.42-1.82]; P < .001), scoring higher on the Somatosensory Amplification Scale (OR, 1.21 [95% CI, 1.06-1.38]; P = .004), and if the vaccine mRNA-1273 was given rather than BNT162b2 (OR, 2.45 [95% CI, 2.01-2.99]; P < .001). No associations were seen for observed experiences.

Conclusions and Relevance

In this cohort study, several nocebo effects occurred in the first week after COVID-19 vaccination. The severity of systemic adverse effects was associated not only with vaccine-specific reactogenicity but also more negative prior experiences with adverse effects from the first COVID-19 vaccination, more negative expectations regarding vaccination, and tendency to catastrophize instead of normalize benign bodily sensations. Clinician-patient interactions and public vaccine campaigns may both benefit from these insights by optimizing and contextualizing information provided about COVID-19 vaccines.

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

BACKGROUND

The Corona pandemic and ongoing mass vaccinations raise the question of the nocebo mechanisms involved. Since immunization is usually administered to healthy people as a preventive health measure, adverse events (AE) following immunization are less accepted and could contribute to vaccine hesitancy. Assuming that vaccinees experience nocebo responses, the aim of this meta-analysis was to investigate the effect sizes of solicited adverse events (or assumed reactogenicity) reported in placebo groups in RCTs on seasonal influenza vaccination.

METHODS

Literature search via PubMed, Web of Science, and CENTRAL was conducted considering gray literature. Only RCTs with placebo groups using pharmacologically inert substances (like saline) were included. Quality was assessed using Cochrane Collaboration's Risk of Bias Tool. Effect sizes were estimated using a random mixed effects model based on k = 31 studies covering 14,326 participants in placebo groups.

RESULTS

Reported solicited AEs in placebo groups showed significant effect sizes of proportions (ES_p). In k = 13 analyzed placebo groups, 35 % of the participants reported at least one solicited systemic AE (p = 0.007). The most common particular solicited systemic AEs were headache (k = 27; 17 %; p = 0.001), malaise (k = 13; 12 %; p = 0.004), and hyperhidrosis (k = 4; 12 %; p < 0.001) within one week after vaccination.

CONCLUSION

The results show significant solicited AEs in placebo groups, indicating substantial nocebo responses after vaccination. Based on the fact that most vaccination programs include similar groups of healthy people, we expect that comparable nocebo effects occur during other campaigns. Health care professionals should be aware of the nocebo response and take action to prevent or decrease the burden of adverse events following immunization. Fear of side effects must be addressed early in order to diminish vaccine hesitancy. Prospero identifier: CRD42020156287, October 2019.

Psychological factors associated with reporting side effects following COVID-19 vaccination: A prospective cohort study (CoVAccS - Wave 3)

OBJECTIVE

To investigate symptom reporting following the first and second COVID-19 vaccine doses, attribution of symptoms to the vaccine, and factors associated with symptom reporting.

METHODS

Prospective cohort study (T1: 13-15 January 2021, T2: 4-15 October 2021). Participants were aged 18 years or older, living in the UK. Personal, clinical, and psychological factors were investigated at T1. Symptoms were reported at T2. We used logistic regression analyses to investigate associations.

RESULTS

After the first COVID-19 vaccine dose, 74.1% (95% CI 71.4% to 76.7%, n = 762/1028) of participants reported at least one injection-site symptom, while 65.0% (95% CI 62.0% to 67.9%, n = 669/1029) reported at least one other (non-injection-site) symptom. Symptom reporting was associated with being a woman and younger. After the second dose, 52.9% (95% CI 49.8% to 56.0%, n = 532/1005) of participants reported at least one injection-site symptom and 43.7% (95% CI 40.7% to 46.8%, n = 440/1006) reported at least one other (non-injection-site) symptom. Symptom reporting was associated with having reported symptoms after the first dose, having an illness that put one at higher risk of COVID-19 (non-injection-site symptoms only), and not believing that one had enough information about COVID-19 to make an informed decision about vaccination (injection-site symptoms only).

CONCLUSIONS

Women and younger people were more likely to report symptoms from vaccination. People who had reported symptoms from previous doses were also more likely to report symptoms subsequently, although symptom reporting following the second vaccine was lower than following the first vaccine. Few psychological factors were associated with symptom reporting.

Drivers of the Intention to Receive a COVID-19 Booster Vaccine: Insights from the UK and Australia

As the global pandemic perpetuates, keeping the population vaccinated will be imperative to maintain societal protection from the SARS-CoV-2 (COVID-19) virus. However, while empirical evidence regarding predictors of the intention to receive a first COVID-19 vaccine has amassed, our understanding regarding the psychological and behavioral drivers of continued COVID-19 vaccination remains limited. In this pre-registered study (UK: AsPredicted#78370|Australia: AsPredicted#81667), factors predicting the intention to receive a COVID-19 booster vaccine were investigated in two adult samples from the UK (N = 1222) and Australia (N = 1197) that were nationally representative on factors of age, gender, and geographic location. High levels of booster intent were found (73% and 67%, respectively). Exploratory Structural Equation Modelling (ESEM) revealed three key predictors of the intention to receive a booster vaccine that emerged across both UK and Australian samples: concern regarding the COVID-19 virus, positive perceptions of the COVID-19 vaccines, and the perceived severity of side effects experienced to the last COVID-19 vaccine dose. Several additional factors (age, months since the last COVID-19 vaccine, familiarity with side effects, and regularly receiving the influenza vaccine) were present in the Australian dataset. These findings provide important evidence that targeting psychological perceptions of the COVID-19 vaccine and virus may serve to maintain participation in the COVID-19 vaccination programme, paving the way for future behavioural research in this area.