Sunday, 16 June, 2024
HomeWeekly RoundupPfizer Inc/BioNTech vaccine's efficacy diminished two-thirds by SA variant

Pfizer Inc/BioNTech vaccine's efficacy diminished two-thirds by SA variant

A laboratory study suggests that the South African variant of the coronavirus may reduce protective antibodies elicited by the Pfizer Inc/BioNTech SE vaccine by two-thirds, and it is not clear if the shot will be effective against the mutation, Reuters reports the companies said. The study found the vaccine was still able to neutralise the virus and there is not yet evidence from trials in people that the variant reduces vaccine protection, the companies said. Still, they are making investments and talking to regulators about developing an updated version of their mRNA vaccine or a booster shot, if needed.

For the study, scientists from the companies and the University of Texas Medical Branch (UTMB) developed an engineered virus that contained the same mutations carried on the spike portion of the highly contagious coronavirus variant first discovered in South Africa, known as B.1.351. The spike, used by the virus to enter human cells, is the primary target of many COVID-19 vaccines.

Researchers tested the engineered virus against blood taken from people who had been given the vaccine, and found a two- thirds reduction in the level of neutralising antibodies compared with its effect on the most common version of the virus prevalent in US trials.

Reuters reports that because there is no established benchmark yet to determine what level of antibodies are needed to protect against the virus, it is unclear whether that two-thirds reduction will render the vaccine ineffective against the variant spreading around the world. However, UTMB professor and study co-author Pei-Yong Shi said he believes the Pfizer vaccine will likely be protective against the variant.

“We don’t know what the minimum neutralising number is. We don’t have that cut-off line,” he said, adding that he suspects the immune response observed is likely to be significantly above where it needs to be to provide protection.

That is because in clinical trials, both the Pfizer/BioNTech vaccine and a similar shot from Moderna Inc conferred some protection after a single dose with an antibody response lower than the reduced levels caused by the South African variant in the laboratory study.

Reuters reports that he noted that even if the concerning variant significantly reduces effectiveness, the vaccine should still help protect against severe disease and death. Health experts have said that is the most important factor in keeping stretched healthcare systems from becoming overwhelmed.

More work is needed to understand whether the vaccine works against the South African variant, Shi said, including clinical trials and the development of correlates of protection – the benchmarks to determine what antibody levels are protective.

Pfizer and BioNTech said they were doing similar lab work to understand whether their vaccine is effective against another variant first found in Brazil.

Moderna published a correspondence with similar data previously disclosed elsewhere that showed a sixfold drop antibody levels versus the South African variant.

 

[link url="https://www.reuters.com/article/us-health-coronavirus-vaccines-variants-idUSKBN2AH2VG"]Full Reuters report (Open access)[/link]

 

[link url="https://www.nejm.org/doi/full/10.1056/NEJMc2102017"]New England Journal of Medicine Pfizer/BioNTech study correspondence[/link]

 

[link url="https://www.nejm.org/doi/full/10.1056/NEJMc2036242"]New England Journal of Medicine Moderna study correspondence[/link]

MedicalBrief — our free weekly e-newsletter

We'd appreciate as much information as possible, however only an email address is required.