A laboratory study indicates that the South African coronavirus variant may decrease by two-thirds the antibody protection of the Pfizer Inc/BioNTech SE vaccine, and it is not clear whether the shot will be effective against the mutation, the companies said on Wednesday.
The study found that the vaccine was still capable of neutralizing the virus and there is still no evidence from human trials that the variant reduces the protection of the vaccine, the companies said.
Still, they make investments and talk to regulators about, if necessary, developing an updated version of their mRNA vaccine or a booster shot.
Scientists from the companies and the University of Texas Medical Branch (UTMB) developed an engineered virus for the study that contained the same mutations carried on the spike portion of the highly contagious coronavirus variant, known as B.1.351, first discovered in South Africa. The spike, used to enter human cells by the virus, is the primary target of many vaccines for COVID-19.
Researchers tested the engineered blood virus taken from people who received the vaccine and found that the level of neutralizing antibodies had decreased by two-thirds compared to its effect on the most common version of the virus prevalent in US trials.
Their findings were published in the New England Journal of Medicine (NEJM).
Since no benchmark has yet been established to determine what level of antibodies are needed to protect against the virus, it is unclear whether the two-thirds reduction will make the vaccine ineffective against the worldwide spread of the variant.
UTMB professor and co-author of the study, Pei-Yong Shi, however, said he believes that the Pfizer vaccine is likely to be protective against the variant.
“We don’t know what the minimum neutralizing number is. We don’t have that cutoff 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 both the Pfizer/BioNTech vaccine and a similar shot from Moderna Inc provided some protection after a single dose in clinical trials with an antibody response lower than the reduced levels in the laboratory study caused by the South African variant.
Even if the related variant reduces efficacy significantly, the vaccine should still help protect against severe illness and death, he noted. That is the most important factor in keeping stretched healthcare systems from becoming overwhelmed, health experts have said.
In order to understand whether the vaccine works against the South African variant, more work is needed, Shi said, including clinical trials and the development of protection correlates – the benchmarks to determine what levels of antibodies are protective.
In order to understand whether their vaccine is effective against another variant first discovered in Brazil, Pfizer and BioNTech said they were doing similar lab work.
On Wednesday, Moderna published a letter in NEJM with similar data previously disclosed elsewhere that showed a sixfold drop in antibody levels compared to the South African variant.
The actual efficacy of its vaccine against the South African variant is still to be determined, Moderna also said. Earlier, the company said it believes that the vaccine will work against the variant.