Vaccine Effectiveness and Epidemiological Impact of SARS-CoV-2 Infections

Vaccination against SARS-CoV-2 has been the cornerstone of the global response to the COVID-19 pandemic, substantially reducing symptomatic infection, hospitalisation and death. Real-world studies have demonstrated high effectiveness of mRNA and viral-vector vaccines across diverse populations, although protection against infection and mild disease wanes over months. Booster doses restore immunity and broaden protection against emerging variants, while differential durability across vaccine platforms informs immunisation schedules. The interplay between population-level coverage and viral circulation has shaped epidemiological trajectories, with undervaccination pockets correlating with surges in severe outcomes. Safety surveillance has confirmed that common adverse events are transient, with rare cardiovascular or thrombotic complications identified only through large-scale record linkage. Attention to equity, global vaccine distribution and variant surveillance remains essential to reduce transmission, prevent health-care overload and guide policy on booster deployment. Integration of real-time infection surveys, cohort analyses and modelling has elucidated the impact of vaccination programmes on community transmission and variant emergence, reinforcing the need for adaptive strategies as the virus evolves.

Research from Nature Portfolio

A large prospective analysis of over 45 million adults in England compared the incidence of arterial and venous thrombotic events before and after first, second and booster doses. Findings showed a net reduction in common cardiovascular complications following vaccination, alongside transient increases in rare events such as vaccine-induced thrombotic thrombocytopenia and mRNA-associated myocarditis. This work supports the favourable risk–benefit profile of all authorised SARS-CoV-2 vaccines and underpins confidence in booster programmes. A foundational community survey examined vaccine effectiveness against the B.1.617.2 (Delta) variant, revealing a 10–16% drop in protection compared with earlier strains and similar peak viral loads in breakthrough and unvaccinated cases. Differences in initial efficacy and waning rates between mRNA and adenoviral-vector vaccines highlighted the need for variant-adapted formulations and informed the timing of additional doses.

Vaccine Effectiveness and Epidemiological Impact of SARS-CoV-2 Infections publication trend

The graph below shows the total number of articles in vaccine effectiveness and epidemiological impact of sars-cov-2 infections across all publications each year (not limited to Nature Index journals).

Technical terms

Vaccine effectiveness: Percentage reduction in disease incidence among vaccinated individuals under real-world conditions.

Breakthrough infection: SARS-CoV-2 infection occurring in a fully vaccinated person.

Waning immunity: Gradual decrease in protective immune response following vaccination.

Variant of concern: Viral lineage with mutations that affect transmissibility, severity or immune escape.

Booster dose: Additional vaccine dose administered after primary immunisation to restore or enhance immunity.

Test-negative design: Epidemiological study method comparing vaccination status of test-positive and test-negative individuals with similar illness symptoms.

References

1. Cohort study of cardiovascular safety of different COVID-19 vaccination doses among 46 million adults in England. Nature Communications (2024).
2. Effect of Delta variant on viral burden and vaccine effectiveness against new SARS-CoV-2 infections in the UK. Nature Medicine (2021).
3. Undervaccination and severe COVID-19 outcomes: meta-analysis of national cohort studies in England, Northern Ireland, Scotland, and Wales. The Lancet (2024).
4. Duration of effectiveness of vaccines against SARS-CoV-2 infection and COVID-19 disease: results of a systematic review and meta-regression. The Lancet (2022).