How should the COVID-19 vaccine be distributed to have the greatest impact on reducing disease risk?
Researchers from the University of New Mexico, the Allende Program for Social Medicine in Albuquerque, and the Global Public Health Institute in India report in a new study of vaccine distribution in different parts of the world that vaccines are most effective when distributed in areas with the highest basic risks.
The peer-reviewed study, published today in the BMJ (British Medical Journal) Evidence-Based Medicine , is believed to be the first study to measure the effectiveness of vaccines in geographic areas in terms of absolute risk reduction.
Vaccines are expensive to obtain and deliver in many low-income countries, and even in low-income areas of wealthier countries. Only 12.9% of people in low-income countries have received at least one dose of a vaccine, compared to 63.1% of the world’s population, a situation sometimes called “vaccine apartheid.” .
Public health systems could assess the baseline risk of contracting COVID-19 by calculating the number of new cases per population, which can be used to determine the absolute risk reduction (ARR) and the number of vaccines needed (NNV) to prevent the symptoms in one person.
These measures allow researchers to determine who could benefit most from vaccination. ARR-based strategies have successfully guided policy decisions on the distribution of other vaccines, such as influenza and pertussis.
Previous studies have shown that ARR and NNV are more useful than relative risk reduction (RRR), which measures effects between groups of people, in evaluating the effect of a treatment or preventive program such as vaccination in populations with different baseline risks. .
The researchers showed that the ARR was larger and the NNV was smaller in two New Mexico counties and two Indian states than elsewhere. This finding suggests that counties and states with lower NNV due to higher baseline risks deserved priority in vaccine distribution.
"As practitioners and teachers of evidence-based medicine, we have been surprised that all published studies of COVID-19 vaccines have reported RRR but not ARR," said Howard Waitzkin, MD, PhD, corresponding author of the paper and distinguished professor emeritus from the University of New Mexico.
“ARR is much more useful for discovering feasible vaccination strategies in areas of the world where access to vaccines remains a big problem,” he said. "Relative measures such as RRR compare a treatment group to a control group without taking into account the populations’ baseline risks."
Without major structural changes to the global economic order, vaccination-related health inequalities are likely to remain a sad reality, the authors argue.
“In this context,” said investigative journalist Ella Fassler, lead author of the article, “public health researchers, policymakers, and community stakeholders can help generate evidence-based vaccine distribution strategies.” and identify barriers that impede these life-saving strategies.
“Targeted programs become important as we face the reality of access barriers related to wealth, power, minority status, structural racism and other sources of deep inequality that prevent much of the world from accessing vaccines.” that save lives.”
