An interesting article published by Cromer and others in The Lancet, November 15 discusses  this issue.  

Several SARS-CoV-2 variants of concern have been identified which partly escape serum  neutralisation elicited by the current vaccines.  

Studies have also shown that vaccines demonstrate reduced protection against symptomatic  infection with SARS-CoV-2 variants. This study explored whether in-vitro neutralisation titres  remain predictive of vaccine protection from infection with SARS-CoV-2 variants. 

This meta-analysis used data from 24 identified studies on in-vitro neutralisation and clinical  protection to understand the loss of neutralisation to the existing SARS-CoV-2 variants of  concern.  

They integrated the results of this analysis into their existing statistical model relating in-vitro  neutralisation to protection. They also analysed data on boosting of vaccine responses and  used the model to predict the impact of booster vaccination on protection against SARS-CoV 2 variants.  

The neutralising activity against the ancestral SARS-CoV-2 was highly predictive of  neutralisation of variants of concern.  

Decreases in neutralisation titre to the alpha, beta, gamma and delta variants were not  significantly different between the different vaccines. Neutralisation remained strongly  correlated with protection from symptomatic infection with SARS-CoV-2 variants of concern  and the existing model remained predictive of vaccine efficacy against variants over time and  this suggested protection against symptomatic infection might decrease below 50% within the  first year after vaccination for some vaccines.  

Boosting of previously infected individuals with existing vaccines is predicted to provide a  higher degree of protection from infection with variants of concern than primary vaccination  schedules alone. 

The geometric mean of the decrease in neutralisation titres was found to be 1.6 fold for alpha, 8·8 fold for beta, 3·5 fold for gamma, and 3·9 fold for delta compared with the ancestral virus.  

Despite the variability in study designs, this meta-analysis found that predicted serological  neutralisation activity against each variant elicited by vaccines was significantly correlated with  protection from symptomatic SARS-CoV-2 infection.

The combined effects of waning immunity and reduced recognition of the SARS-CoV-2  variants of concern suggested that vaccine boosters would be needed to maintain protection  of more than 50% against symptomatic SARS-CoV-2 infection. This analysis suggested that  maximising neutralising antibody responses to the ancestral virus, through booster  vaccinations of previously infected individuals should be an effective strategy to broadly  increase neutralisation titres against SARS-CoV-2 variants.  

In conclusion, this analysis suggests that good protection against the current variants of  concern could be achieved by vaccination with existing vaccines using ancestral spike targets  and the boosting with these vaccines is probably an effective strategy to combat the waning of  immunity and the current variants of concern.  

In the future, vaccines targeting novel variants of concern would be required if highly escaped variants arrive, but existing vaccines provide an effective method for boosting immunity  against the current variants of concern. 

The London General Practice the leading London doctors’ clinic in Harley Street commends  the government on its vaccination program and encourages all those eligible to have their  initial vaccines and to have their booster doses. 

Dr Paul Ettlinger 

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