Pfizer COVID-19 vaccine might still overcome UK and SA variants

Simon Collins, HIV i-Base

The continued efficacy of current COVID-19 vaccines against two recent variants with multiple mutations in the S spike is an important and early concern.

Both recent variants linked to higher rates of transmission – B.1.1.7 in the UK and B.1.351 from South Africa – share the N501Y substitution in the S spike region. Similar unrelated variants have also been recently reported  in Japan and Nigeria. [1]

An analysis published on 7 January 2021 from Pfizer reports likely continued activity for the their mRNA vaccine. However, the standard cautions apply for this paper not yet having been peer reviewed. [2]

The study reported continued impact on 16 isogenic viruses (essentially similar) developed with N501Y and tested immune response to these in samples from 20 participants who had previously received the Pfizer vaccine. These samples showed similar neutralising titres to both mutated and consensus viruses.

A limitation included in the paper includes that the N501Y viruses did not contain the full range of mutations in the UK and SA variants.

It also reported that the flexibility of mRNA technology would be able to respond to future emerging variants that might reduce vaccine responses. Continued ongoing surveillance research will be important for identifying new variants.

A letter to CID also reported a case of reinfection involving critical illness with the UK variant in a 78 year old man with multiple comorbidities who had previously experienced mild COVID-19 during the first wave in April 2020. [3]

The variant itself might not be the cause of the more serious outcomes as numerous cases of secondary infections with different outcomes have previously been reported before the recent variants. [4]

The letter also notes that this might also be the results of waning antibody responses from the first infection. However, antibody responses tend to be highest in people with severe infection, which in this case was mild.


  1. Johns Hopkins COVID-19 updates. (12 January 2021).
  2. Xie X et al. Neutralization of N501Y mutant SARS-CoV-2 by BNT162b2 vaccine-elicited sera. BioRxiv. DOI: 10.1101/2021.01.07.425740. (7 January 2021).
  3. Confirmed reinfection with SARS-CoV-2 variant VOC-202012/01. Clinical Infectious Diseases. ciab014. DOI: 10.1093/cid/ciab014 (09 January 2021).
  4. COVID-19 reinfection can occur after varying times and with more severe disease. HTB (14 October 2020).

This report was first posted on 10 January 2021.

Links to other websites are current at date of posting but not maintained.