Any updates on the vaccine’s efficacy against the new variants?


A. Yes, and there’s reason for cautious optimism!

In a recently published pre-print (not yet peer-reviewed), the Pfizer-BioNTech vaccine appeared to generate a strong antibody response against the tested variants, including B1.1.7 (first identified in the UK) and B1.351 (first identified in South Africa). But these promising findings were primarily found among subjects vaccinated with BOTH doses.

Nevertheless, even one vaccine dose, or prior COVID-19 infection, appeared to at least induce a T cell response to the variants. T cells are a component of the immune system that work to destroy virus-infected cells and support the production of antibodies. They are generally not enough to prevent infection and even illness, but as Dr. William James, lead scientist on the study notes in the linked news article below, “it does suggest there’s something to work from and that your immune system can respond to [the variants].”

➡️What was done in the study?

Researchers at the University of Oxford took blood samples from people previously infected with COVID-19 in the UK in Spring 2020, and from individuals vaccinated after 1 and after 2 doses of the Pfizer-BioNTech vaccine. In a laboratory setting, they then tested for antibody and T cell responses in these blood samples after exposing the samples to the UK and South African variant, as well as the older variant that was circulating in 2020 (B VIC01).

➡️Key results:

T cell activity was detected in the blood samples of COVID-19 survivors, for people after 1 shot, and for people after 2 shots of the Pfizer-BioNTech vaccine. Importantly, this T cell activity was detected against all 3 variants.

However, there were large differences in antibody response across the 3 groups of blood samples, and depending on the variant:

✳️For COVID-19 survivors: antibody responses were lowest against the 2 newer variants among people that had been naturally infected with COVID-19 compared to people receiving 1 or 2 doses of the vaccine. For people with low levels of antibody from past infection, antibody responses against either of the newer variants were undetectable. People with a stronger antibody response from past infection showed some level of neutralization of the UK variant, but much less so for the South African variant.

✳️After 1 shot: There was some antibody response to the UK variant, but antibody response against the South African variant was undetectable.

✳️After 2 shots: Although antibody response to the South African variant was lower than for the older variant, in over 90% of the subjects, levels remained high enough to theoretically protect against symptomatic illness. Protection was also high against the UK variant.

➡️What does this mean clinically?

COVID survivors and people with only 1 shot of the Pfizer-BioNTech vaccine can still become infected and have symptoms, especially after exposure to the new variants. But because T cell response was preserved, it’s possible they may not get as sick as they would have before infection or before vaccination.

People with 2 shots seemed to have the most protection as indicated by the combination of T cell and antibody response to the variants. Scientists believe this may lead to less symptomatic disease among people vaccinated with 2 shots if exposed to the UK and South African variants.

*****It’s important to note that this study did not assess whether people got infected with COVID-19 or whether they developed symptomatic illness. We only know how their immune cells responded when their blood samples were exposed to the variants in a lab. So caution is warranted in applying these findings to the real world, and in other populations, but we can still be excited by the possibility!

Those Nerdy Girls


Study preprint

Related news article

Link to original FB post