- New evidence indicates that the Pfizer jab is effective against highly infectious SARS-CoV-2 variants, including the one circulating in SA
- The study's researchers tested the two-dose vaccine against six variants
- Since this was a lab study, it remains to be seen whether the results will translate in a clinical setting
The Covid-19 vaccine developed by Pfizer-BioNTech provides “very strong protection” against the original virus variant, as well as the newer variants, researchers of a recently published study found.
Their work, reported in mBio, an open-access journal of the American Society for Microbiology, tested the vaccine against the following six different variants in the laboratory:
- Alpha (B.1.1.7 or 501Y.V1) first detected in the UK
- Beta (B.1.351 or 501Y.V2) first detected South Africa
- Gamma (P.1 or 501Y.V3) first detected in travellers from Brazil
- COH.20G/677H, first detected in Columbus Ohio
- 20A.EU1, first detected in Spain
- The mink cluster 5 spike proteins located in minks in Denmark
"The vaccines provide very strong protection against the earlier forms of the virus as well as the newer variants,” Nathaniel Landau, professor in the Department of Microbiology at the NYU Grossman School of Medicine, New York City, said in a press release.
He added: “This is an important point because I have heard people say that they don't think there is a reason to get vaccinated, because the vaccine isn't going to work against the variants, but that is not true – the vaccine will work against the variants.”
The highly contagious Beta variant is currently dominating infections in South Africa and has spread to at least 20 other countries, while the Alpha variant is becoming the dominant virus in many parts of the world, and is considered to be potentially deadlier than the original virus first identified in Wuhan, China. The latest data showing that the Pfizer vaccine performs well against these variants are, therefore, reassuring.
Testing the jab against variants
The research team created a panel of pseudotype viruses that combined the HIV virus and SARS-CoV-2 spike protein (responsible for the virus entering the cells and causing infection).
“The SARS-CoV-2 spike protein is important, because it is the only structure on the virus that is exposed to the outside … it is what sticks out from the virus; it is what the immune system recognises and what allows the virus to stick onto target cells,” said Landau.
Pseudotype viruses, the authors explained, are viral particles that are replicated and have been proven to be useful as research tools, are easy to work with in the lab, and come with minimal risks.
Following this, they created a panel of pseudotype viruses using the spike proteins from the six different variants of SARS-CoV-2. The pseudotype viruses were mixed with serum from either people who had received the Pfizer vaccine or people who had already had Covid infection.
'Vaccine antibodies powerful'
The Pfizer vaccine was found to work as well against the majority of variants as the original virus variant, although the vaccine was less effective against the Beta and Gamma variants due to a particular mutation. It neutralised these two variants with a 3-fold decrease in titer (titer refers to a lab test that measures the level of antibodies in a person’s blood sample).
However, Landau said that people shouldn’t be concerned about this result.
"Our interpretation of the results is that the vaccine antibodies are very powerful, and even if you lose 3-fold of the titer, there is still plenty of antibody there to neutralise the virus.”
The team said similar results were applicable to the Moderna vaccine, which uses the same mRNA technology, although those results were not reported in their paper.
They raised the point of uncertainty on whether their lab findings will translate into clinical effect when human volunteers are infected with one of the variants. “We cannot say for sure. We will only know when the clinical data come in," they said.
The Pfizer vaccine is currently being administered in South Africa. The vaccine requires two doses in order for it to be most effective against Covid disease. As of 8 June, more than 1.5 million South Africans had received at least one dose of the jab, Business Insider SA reported.READ | Three for three: Understanding the 3 Covid-19 variants circulating during SA’s third wave