In a new study from Public Health England and elsewhere, researchers found that Pfizer’s coronavirus vaccine provides surprisingly robust protection against the highly infectious Delta variant of COVID-19—but only if people have gotten both doses.
They found that two doses of the messenger RNA (mRNA) vaccine is 88% effective in protecting people against the Delta variant, compared with about 94% effectiveness against the original strain of COVID.
However, effectiveness among people who only got one dose was much lower, only around 31%.
The team says the data is mounting that the mRNA vaccines are the solution to the Delta variant. It is also apparent that the second dose of these vaccines is needed to augment the immunity from the first dose, for a person to be resilient to the variant.
The Delta variant has developed seven different mutations in the coronavirus’ “spike” protein, compared to the original Alpha strain.
Vaccines will only remain effective if they can withstand such attempts by the coronavirus to evolve around the immune system defenses created by inoculation.
In the case of the Pfizer vaccine, it appears that the two-dose series produces protection that can withstand the Delta variant’s mutations.
This is likely because two doses create a lot more antibodies. Antibodies that don’t work as well can still work, especially if you have enough of them.
This study evaluated all COVID-19 cases in the United Kingdom through May, with researchers checking to see if the infected folks have been previously vaccinated.
They found vaccine effectiveness against hospitalization for the Delta variant is uniformly high for the Pfizer vaccine.
These results are even more impressive because they’re occurring in real-world situations, rather than in carefully controlled clinical trials.
Researchers say that two-dose vaccines employ a prime-boost strategy, in which the first dose makes the immune system aware of a harmful virus or bacteria, and the second dose dramatically amps up future response by prompting the body to produce a lot more immune cells.
On top of having more antibodies, people who’ve gotten the second dose also might have immune cells that are prepared to attack the coronavirus in a broader variety of places.
The study is published in the New England Journal of Medicine. One author of the study is Jamie Lopez Bernal.
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