The global landscape of SARS-CoV-2 has changed dramatically since the onset of the COVID-19 pandemic, as have our questions about the role and impact of vaccines. Population-level immunity against the virus has increased due to widespread vaccination and infection, resulting in significant declines in severe disease and death across all age groups.
However, SARS-CoV-2 continues to evolve with new immune-evasive Omicron subvariants emerging regularly posing continued risks to vulnerable populations. Monitoring the effectiveness of existing and updated COVID-19 vaccines is still needed to inform vaccination policy and recommendations.
Purpose and value of an ongoing systematic review
Systematically reviewing the performance of COVID-19 vaccines in the real world, that is, beyond the controlled settings of clinical trials, addresses important questions including how long protection from COVID-19 vaccines lasts, how well the vaccines perform in vulnerable populations and against new SARS-CoV-2 (sub)variants, and how well new vaccines targeting recent (sub)variants protect against disease.
The COVID-19 Vaccine Effectiveness project, conducted by the International Vaccine Access Center (IVAC) at the Johns Hopkins Bloomberg School of Public Health, draws upon well-established expertise in epidemiology, vaccine evaluation, immunology, and surveillance to summarize and synthesize the results of both vaccine effectiveness and vaccine neutralization studies, which assess the capacity of antibodies in the blood to block SARS-CoV-2 infection. This high-quality ongoing systematic review has been and continues to be used by regional and global policymakers.
Regularly updated results of the review and simplified visualisations of vaccine effectiveness and neutralization data are made publicly available at https://view-hub.org/vaccine/covid/resources.
Regional and global vaccine policies
Key stakeholders of this endeavour beyond CEPI include the World Health Organization (WHO), regional immunisation advisors, governmental agencies, pharmaceutical industry, regulators, academic institutions, funding agencies, manufacturers, and non-governmental organisations. WHO regularly shares these data regionally and globally, ensuring that recommendations are grounded in the latest vaccine effectiveness evidence:
WHO’s Technical Advisory Group on COVID-19 Vaccine Composition (TAG-CO-VAC) regularly reviews vaccine effectiveness data to update statements on vaccine performance against emerging (sub)variants. The most recent statement recommended a transition to a JN.1-containing monovalent vaccine formulation.
WHO’s Strategic Advisory Group of Experts on Immunization (SAGE) has a working group on COVID-19 vaccines that regularly reviews COVID-19 vaccine effectiveness data to inform their global policymaking. The most recent global recommendation is the “WHO SAGE Roadmap for Prioritizing Use of COVID-19 Vaccines," updated on November 10, 2023, which incorporates evidence from Omicron-specific VE studies (up-to-date evidence is accessible on https://view-hub.org/vaccine/covid/).
WHO’s Department of Immunization, Vaccines, and Biologicals communicates these updates to WHO regional colleagues and the WHO Health Emergencies programme. This communication takes place by sharing vaccine effectiveness data in weekly summary tables, monthly epidemiological reviews, stakeholder forums, and study methods forums which reach a broad audience globally (academic institutions, government agencies, the pharmaceutical industry, regulatory bodies, manufacturers, and NGOs). Please see the Project Impact report for further details.
Publications
Various publications from this project on the effectiveness and neutralization capacity of COVID-19 vaccines are available here.
Safety project
A parallel collaboration between CEPI, the COVAX vaccine safety working group and the WHO Pharmacovigilance team, in partnership with IVAC at Johns Hopkins Bloomberg School of Public Health, revealed gaps in capacity to assess the safety of many COVID-19 vaccines used by low- and middle-income countries. The COVID-19 vaccine safety study provides evidence of the need to invest in networks and platforms for generating active safety surveillance in preparation for the next pandemic. Please see this Brighton collaborative article for further details.
