Pfizer Covid shot protects people from hospitalization even as effectiveness against infection falls, Lancet study confirms

The effectiveness of Pfizer and BioNTech’s Covid-19 vaccine against infection tumbles over several months, falling from a peak of 88% a month after receiving the two-shot series to 47% six months later, according to an observational study published Monday in the peer-reviewed journal The Lancet.

While the two-dose mRNA vaccine’s efficacy against infection wanes, its protection against Covid-related hospitalizations persists, remaining 90% effective for all coronavirus variants of concern — including delta — for at least six months, according to the study, which was funded by Pfizer.

The findings confirm early reports from the Centers for Disease Control and Prevention and Israeli health officials that found the protection against infection falls over several months even as its effectiveness in keeping people out of the hospital held up.

“Protection against infection does decline in the months following a second dose,” said Dr. Sara Tartof, an epidemiologist at Kaiser Permanente and the study’s lead author. Kaiser Permanente conducted the research with Pfizer.