Herd different

In Last Wednesday’s Scotsman Conor Matchett reported that “Scotland is ‘nudging towards’ herd immunity as it approaches winter”. Additionally, Jillian Evans of NHS Grampian reportedly said ‘that “herd immunity – where enough people have enough immunity to a virus that its ability to transmit and reinfect is limited – was getting closer.”

An article in The Lancet Microbe of 1 October points to insufficient immunity following re-infection to stop transmission following infection recovery. It states: “The estimated median time to reinfection following peak antibody response for SARS-COV-2 is 16 months (roughly half of infected persons re-exposed to the virus would be re-infected within 16 months). In particular, our estimate argues strongly against the claim that a long-standing resolution of the epidemic could arise due to herd immunity from natural infection. Our results caution that reinfection will become increasingly common as pandemic disease transitions into endemic disease.”

The concept of herd immunity is best applied where the large majority of a population cannot transmit a disease due to lifetime immunity either because of vaccination or prior infection. This is not the case with Covid-19. It seems that current attempts to achieve herd immunity from Covid-19 are very unlikely to succeed. A real solution would be to improve vaccines to confer long-term immunity from disease transmission, else we must reconfigure society so transmission is largely eliminated to avoid the current 8,665 Scottish death toll endlessly increasing.

KEN CAREW

Dumfries