The study showed the effectiveness of the vaccine against the Brazil strain was ‘roughly equivalent’ to the virus without mutations.
New, highly transmissible SARS-CoV-2 variants are spreading globally: including those first identified in the UK (B.1.1.7 lineage), South Africa (B.1.351 lineage), and most recently Brazil (P.1 lineage).
With mutations found on the spike protein – the target of most vaccines – it has raised the question of how effective vaccines are against such mutations.
A lab study from the University of Texas Medical Branch engineered an early isolate of the virus to contain the same spike protein mutations as the above variants. Scientists tested 20 serum samples from 15 participants from Pfizer’s Phase 3 trial against each virus, either two or four weeks after the administration of the second dose of BNT162b2.
They found that all the serum samples ‘efficiently neutralised’ both the base early isolate of the virus from January 2020 (USA-WA1/2020) and all viruses with variant spikes.
“Compared with neutralization of USA-WA1/2020, neutralization of B.1.1.7-spike and P.1-spike viruses was roughly equivalent, and neutralization of B.1.351-spike virus was robust but lower,” note the authors.
The lab study was only able to assess certain aspects of the response prompted by vaccines; and the authors note that real-world evidence will need to be gathered.
Other early studies have suggested that the vaccine is effective against the South Africa and UK strains; although Pfizer and BioNTech have also started trialing the effectiveness of a third booster dose to the current two-dose regimen in providing protection against virus variants. The companies also say the mRNA platform can be easily used to modify the vaccine against new variants if required.
Virus mutations are emerging as expected: but the ones which cause the most concern are the ones that change the virus’ spike protein. This is because it is the spike protein that helps the virus enter human cells, and is the part of the virus that most vaccines target.
UK (B.1.1.7): spike protein mutation N501Y
South Africa (B.1.351): multiple spike protein mutations, including K417N, E484K, N501Y
Brazil (P.1): three spike protein mutations, K417T, E484K, and N501Y
The N501Y mutation appears to be linked to increased transmission; while the E484K mutations may affect the body’s antibody response.