September 13, 2021

expert reaction to viewpoint article on COVID-19 booster vaccines for general populations

An article, published in The Lancet, discussed COVID-19 booster vaccines for general populations. 

Prof Azra Ghani, Chair in Infectious Disease Epidemiology, Imperial College London, said:

“The paper presents a very thorough review of studies on the efficacy and effectiveness of COVID-19 vaccines.  When considering the value of booster doses however, it is important that the full potential effect of such a boost is taken into account.  For all vaccines, there is an element of direct and indirect impact.  The former is the individual protection against severe disease whilst the latter is the effectiveness of the vaccine at preventing infection and onward transmission which in turn protects vulnerable people who may have lower protection (such as the immunocompromised).  Whilst it is clear that the effectiveness of current vaccines against severe disease has only slightly reduced with the emergence of the delta variant, there has been a significant reduction in their effectiveness against infection.  Furthermore, there is emerging evidence of waning of efficacy against both endpoints that broadly mirrors the waning of antibody titres.

“These reductions may appear to be numerically small.  But it is important to bear in mind that when applied across a population, even a reduction from 95% to 90% can result in a substantial increase in cases requiring hospitalisation in the absence of other non-pharmaceutical interventions.  Similarly a reduction in vaccine efficacy against infection will substantially increase transmission and hence the risk to both vaccinated and unvaccinated individuals.  Even in the most developed countries, these small differences can put a severe strain on the health system.  There is therefore no “one size fits all” approach to booster vaccines as implied here, nor should such a strategy be described as “high-stakes”.  As the authors conclude, countries should use current best evidence to assess their benefits.  As part of this evaluation, it is important that both the direct and indirect impact of the proposed vaccination strategy is captured.”

‘Considerations in boosting COVID-19 vaccine immune responses’ by Philip R Krause et al. was published in the Lancet at 14:00 UK time on Monday 13 September 2021.

DOI: 10.1016/S0140-6736(21)02046-8

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Declared interests

None received.