COVID-19 vaccination breakthrough infections in a real-world setting: Using community reporters to evaluate vaccine effectiveness (preprint)

Background COVID-19 has highlighted the need for new methods of pharmacovigilance. Here we use community volunteers to obtain systematic information on vaccine effectiveness and the nature and severity of breakthrough infections. Methods Between December 15, 2020 to September 16, 2021, 10,412 unpaid community-based participants reported the following information to an on-line registry: COVID-19 test results, vaccination (Pfizer, Moderna, or Johnson & Johnson), COVID-19 symptoms and perceived severity using a 4-point scale. COVID-19 infections were described for those who were 1) fully vaccinated, 2) partially vaccinated (received first of two dose vaccines or were <14 days post-final dose), or 3) unvaccinated. Results Of 8,554 who were vaccinated, COVID-19 infections were reported by 74 (1.0%) of those who were fully vaccinated and 198 (2.3%) of those who were partially vaccinated. Among the 74 participants who reported a breakthrough infection after full vaccination, the median time to reported positive test result was 104.5 days (Interquartile range: 77-135 days), with no difference among vaccine manufactures. One quarter (25.7%) of breakthrough infections in the fully vaccinated cases were asymptomatic. More than 97% of fully vaccinated participants reported no moderate/severe symptoms compared to 89.3% of the unvaccinated cases; and only 1.4% of fully vaccinated participants reported experiencing at least 3 moderate to severe symptoms compared to 7.8% in the unvaccinated. Conclusion Person-generated health data, also referred to as patient-reported outcomes, is a useful resource for quantifying breakthrough infections and their severity, showing here that fully vaccinated participants report no or very mild COVID-19 symptoms.

Evaluating Real-World COVID-19 Vaccine Effectiveness Using a Test-Negative Case-Control Design (preprint)

It is important to assess the extent to which the real-world effectiveness of marketed vaccines is consistent with that observed in the clinical trials, and to characterize how well vaccines prevent COVID-19 symptoms. We conducted a modified test-negative design (TND) to evaluate the RW effectiveness of three COVID-19 vaccines by leveraging data from an on-going, US community-based registry. Vaccine effectiveness was examined in two ways: considering cases who (1) tested positive for COVID-19 (695 cases, 1,786 controls) and who (2) tested positive with at least one moderate/severe COVID-19 symptom (165 cases, 2,316 controls). Any vaccination (full or partial) was associated with a 95% reduction in the odds of having a positive COVID-19 test [adjusted odds ratio (aOR) = 0.05 (95% confidence interval (CI): 0.04, 0.06)]. Full vaccination was associated with an aOR of 0.03 (95% CI: 0.03, 0.05) while partial vaccination had an aOR of 0.08 (95% CI: 0.06, 0.12). Any vaccination was associated with a 71% reduction in the odds of testing positive and having at least one moderate/severe symptom (aOR=0.29 (95% CI: 0.20, 0.40)). High effectiveness was observed across all three vaccine manufacturers both for prevention of positive COVID-19 test results and prevention of moderate/severe COVID-19 symptoms.

How frequent are acute reactions to COVID-19 vaccination and who is at risk? (preprint)

Introduction: Our objective was to describe and compare self-reported side effects of COVID-19 vaccines in the USA. Methods: A web-based registry enrolled volunteers who received a COVID-19 vaccine between March 19 and July 15, 2021. We collected self-reported short-term side effects, medical consultation, hospitalization, and quality of life impact following completed vaccination regimens (Pfizer, Moderna, J&J). Results: We recruited 6,966 volunteers who completed their full course of vaccination (median age 48 years, IQR 35.0-62.0; 83.6% female): Pfizer 3,486; Moderna 2,857; J&J 623. Few (3.1%) sought medical care for post-vaccination side effects. Hospitalization (n=17; 0.3%) and severe allergic reactions (n=39; 0.6%) also were rare. Those with autoimmune disease or lung disease were approximately twice as likely to seek medical care (adjusted odds ratio (aOR) 2.01 [95% CI: 1.39;2.92] and 1.70 [95% CI: 1.12;2.58] respectively). 92.4% of participants reported >1 side effect (median 3), with injection site reactions (78.9%), fatigue (70.3%), headache (49.0%) reported most frequently. More side effects were reported after the second dose of two-dose vaccines (medians: 1 vs. 2 for Pfizer and 1 vs. 3 for Moderna for first and second doses respectively) versus 3 for J&J's single-dose vaccine. For the employed, the median number of workdays missed was one. Diabetics and those vaccinated against influenza were substantially less likely to report >3 symptoms (aOR 0.68, 95% CI 0.56,0.82 and aOR 0.82, 95% CI 0.73,0.93, respectively.) Discussion: The total side effect burden was, not unexpectedly, greater with two-dose regimens but all three vaccines appear relatively safe. Very few subjects reported side effects serious enough to warrant medical care or reported post-vaccination hospitalization. While these findings do not address possible long-term effects, they do inform on their short-term safety and tolerability and will hopefully provide some reassurance and positively inform the benefit-risk and pharmacoeconomic assessment for all three vaccines. Clinicaltrials.gov NCT04368065