Importance of booster vaccine to protect against emergent COVID-19 variants

Kirk Taylor, HIV i-Base

A small study showing the importance of booster vaccination to protect against COVID-19 variants by researchers from Ohio University was published as a letter in the 15 June edition of the NEJM. [1]

Neutralising antibody (nAb) titres against different COVID-19 strains were analysed from stored serum samples. Participants were healthcare workers that had been triple vaccinated with Moderna (n=4) or Pfizer (n=11) mRNA vaccines. Additional samples from people admitted to ICU during the delta wave (n=18) or hospitalised during omicron wave (n=30) were also studied.

Compared to the D416G COVID-19 strain, nAb titres were 4.1-fold and 3.2-fold lower against BA.4/5 and BA.2.12.1 variants, respectively (p<0.001).

Overall, nAb titres against emergent strains were lowest in twice vaccinated participants. Boosting or previous COVID-19 disease generated greater levels of nAbs compared to unboosted individuals.


This is a short letter to NEJM that concerns an important topic, but it is important to note that the sample sizes are low.

Boosting of immune responses following COVID-19, is strain-dependent. A study of 700 triple vaccinated healthcare workers in the UK reports that immune boosting is lower for omicron than compared to other variants. [2]

These data highlight the importance of receiving COVID-19 boosters as required by local vaccination programmes.


  1. Qu P et al. Neutralization of the SARS-CoV-2 omicron BA.4/5 and BA.2.12.1 subvariants. NEJM. DOI: 10.1056/NEJMc2206725 (15 Jun 2022).
  2. Reynolds CJ et al. Immune boosting by B.1.1.529 (Omicron) depends on previous SARS-CoV-2 exposure. Science. DOI: 10.1126/science/abq1841 (14 Jun 2022).

This report was first published on 26 June 2022.

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