A group of British experts has assessed that vaccination campaigns against COVID-19 are likely to continue for several years as the immunity resulting from vaccines will wane over time. 

The Scientific Advisory Group for Emergencies, which is advising the British government on COVID-19, published its report last Friday under the title “How long will vaccines continue to protect against COVID-19?”

In the report, the British experts on infectious diseases said they can't tell what the optimal required frequency for re-vaccination would be to protect the vulnerable from COVID-19. 

The report said it could be expected that effectiveness will remain high for severe disease, though it could fall over time against mild disease and infection, citing reports from the U.K. and Israel that support its assertions.

Israel, which rolled out a comprehensive and early vaccine campaign, has begun administering booster shots of the Pfizer vaccine to people aged 60 or older as part of efforts to curb the spread of the Delta variant.