LONDON - As the highly contagious delta variant continues to spread, a new, British study shows COVID-19 vaccines are effective against the delta variant, but that their protection decreases over time, weakening significantly within three months.According to the pre-print study, investigators with Oxford University and the United Kingdom’s Office for National Statistics found that those who get infected with COVID-19 after receiving two shots of either the Pfizer-BioNTech or the AstraZeneca vaccine may be of greater risk to others than with previous variants of the coronavirus.The investigators looked at data from more than 2.58 million swab PCR tests taken between Dec.