COVID-19 vaccines against the now prevalent Delta variant of the coronavirus weakens within three months.It also found that those who get infected after receiving two shots of either the Pfizer-BioNTech or the AstraZeneca vaccine may be of greater risk to others than under previous variants of the coronavirus.
Travellers double up on COVID-19 vaccine as Delta variant spreads through U.S. Based on more than three million nose and throat swabs taken across Britain, the Oxford University study found that 90 days after a second shot of the Pfizer or AstraZeneca vaccine, their efficacy in preventing infections had slipped to 75% and 61% respectively.That was down from 85% and 68%, respectively, seen two weeks after a second dose.