Coronavirus vaccines made by Moderna and Pfizer continue to be more than 90% effective, based on various studies, a US Centers for Disease Control and Prevention official said Wednesday.
A review of the efficacy of mRNA vaccines – those that use messenger RNA to deliver immunity – shows two doses provide strong immunity in a variety of groups, Dr. Katherine Fleming-Dutra of CDC’s respiratory diseases branch told a meeting of the CDC’s Advisory Committee on Immunization Practices.
A single dose is less effective, the studies have shown.
“Initial COVID-19 vaccine effectiveness estimates from recently published reports are demonstrating remarkably consistent results across studies with a variety of methods and populations,” Fleming-Dutra said.
Studies are ongoing, she added.
“An important vaccine effectiveness priority is to understand the duration of protection provided by Covid-19 vaccines,” she added. “This will inform the question about the need for a booster.”
Another factor – new variants. So far, none seem to greatly affect the effectiveness of vaccines.
“It is important to take into account changes in the circulating variants over time,” Fleming-Dutra said.