The U.S. Food and Drug Administration (FDA) on June 3 recommended updating the formulation of the COVID-19 vaccines because of studies that indicate their effectiveness is worse against circulating variants of SARS-CoV-2, the virus that causes COVID-19.
“In prior years there appears to have been an inverse relationship between the time since vaccination and vaccine effectiveness, such that COVID-19 vaccine effectiveness against SARS-CoV-2 sublineages appears to wane over time and that better matching of the vaccine to circulating strains is associated with improved neutralizing antibody titers,” FDA staffers wrote in a briefing document, citing two studies.
