Balancing Benefits and Harms of COVID-19 Vaccines: Lessons from the Ongoing Mass Vaccination Campaign in Lombardy, Italy

Abstract

Background. Limited evidence exists on the balance between the benefits and harms of the COVID-19 vaccines. The aim of this study is to compare the benefits and safety of mRNA-based (Pfizer-BioNTech and Moderna) and adenovirus-vectored (Oxford-AstraZeneca) vaccines in subpopulations defined by age and sex. Methods. All citizens who are newly vaccinated from 27 December 2020 to 3 May 2021 are matched to unvaccinated controls according to age, sex, and vaccination date. Study outcomes include the events that are expected to be avoided by vaccination (i.e., hospitalization and death from COVID-19) and those that might be increased after vaccine inoculation (i.e., venous thromboembolism). The incidence rate ratios (IRR) of vaccinated and unvaccinated citizens are separately estimated within strata of sex, age category and vaccine type. When suitable, number needed to treat (NNT) and number needed to harm (NNH) are calculated to evaluate the balance between the benefits and harm of vaccines within each sex and age category. Results. In total, 2,351,883 citizens are included because they received at least one dose of vaccine (755,557 Oxford-AstraZeneca and 1,596,326 Pfizer/Moderna). A reduced incidence of COVID-19-related outcomes is observed with a lowered incidence rate ranging from 55% to 89% and NNT values ranging from 296 to 3977. Evidence of an augmented incidence of harm-related outcomes is observed only for women aged <50 years within 28 days after Oxford-AstraZeneca (being the corresponding adjusted IRR of 2.4, 95% CI 1.1–5.6, and NNH value of 23,207, 95% CI 10,274–89,707). Conclusions. A favourable balance between benefits and harms is observed in the current study, even among younger women who received Oxford-AstraZeneca.

Increased risk of myocarditis and pericarditis and reduced likelihood of severe clinical outcomes associated with COVID-19 vaccination: a cohort study in Lombardy, Italy

“…This issue was of particular concern at the beginning of the vaccination campaign, when pharmacovigilance studies suggested that adenovirus-vectored vaccines could have been responsible of rare thromboembolic events [8,9]. However, a population-based cohort study conducted in the same setting as compared to the current study, aimed to evaluate the balance between benefits and harms of citizens vaccinated with available adenovirus-vectored vaccines, found a favourable risk benefit profile [10].…”

“…The novel approach used in this study for evaluating the balance between harms and benefits of anti-COVID-19 vaccines was previously used in a similar setting, for evaluating a potential increased risk of thromboembolic events in individuals who received the adenovirus-vectored vaccines [10]. In the current study, an unfavourable balance between harms and benefits for men 16 to 19 years of age who received the Moderna vaccine was highlighted.…”

“…Different metrics were used to compare the harms and benefits of vaccine exposure. In particular, the NNH was considered the number of individuals who would need to be vaccinated to generate a case of myocarditis, while the NNT was considered the number of individuals who should be vaccinated to avoid a case of severe COVID-19 disease [10]. Therefore, a desirable vaccination profile was defined as a low NNT and a high NNH [31].…”

Knocking on heaven's door: The gap between health institutions and academies in generating knowledge utilizing real-world data

“…Fourth, what harms are associated with COVID-19 vaccines and how can rare, serious adverse effects be explained, predicted, and avoided? ( 17 ). Lastly, what is the actual duration of vaccine-dependent protection and how can we measure the various components and overall efficacy of vaccination?…”