The effectiveness of the Pfizer-BioNTech vaccine against infection by COVID-19 falls to 47% six months after the second vaccine dose, a new study shows.
The peer-review analysis, which was published in the Lancet medical journal, found that two doses of the vaccine were 90% effective against COVID-19 hospitalisation for at least six months, but only 47% effective against infection after that period.
Researchers analysed the electronic health records of 3.4 million people who had received the Pfizer-BioNTech vaccines.
The reduction in the vaccine’s effectiveness against COVID-19 infection was due to its waning over time and not because of Delta or other variants, the study found.
"Our variant-specific analysis clearly shows that the BNT162b2 vaccine is effective against all current variants of concern, including Delta," said Dr Luis Jodar, chief medical officer at Pfizer Vaccines.
"COVID-19 infections in people who have received two vaccine doses are most likely due to waning and not caused by Delta or other variants escaping vaccine protection."