A British public health study has found that protection from either of the two most commonly used 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.

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 percent and 61 percent respectively.

That was down from 85 percent and 68 percent, respectively, seen two weeks after a second dose. The decline in efficacy was more pronounced among those aged 35 years and older than those below that age.