The trickle of Omicron data is quickly becoming a fountain ⛲.
On the heels of yesterday’s Omicron studies, (see summary here) Pfizer today released data showing strong neutralization of Omicron after 3 doses of its vaccine, but a significant reduction for 2 doses.
➡️ 2 doses showed significantly reduced neutralization titers against Omicron.
➡️ A 3rd dose of Pfizer/BioNTech increased the neutralizing antibody titers against Omicron by 25-fold compared to 2 doses.
➡️ Antibody levels after the booster dose were comparable to levels observed after 2 doses against the original variant.
➡️ The company also reports that a 3rd dose strongly increases CD8+ T cell levels against multiple spike protein epitopes which correlate with the protection against severe disease. Most of these epitopes remain unchanged in the Omicron spike variant compared to the original variant.
The study used blood from people vaccinated with either 2 or 3 doses of the Pfizer vaccine. This blood was collected 3 weeks after the 2nd dose or 4 weeks after the 3rd dose.
The scientists tested how well this blood could neutralize a “pseudovirus” made to mimic Omicron in a lab dish. A pseudovirus as the name suggests is a fake version of the real thing that can’t replicate and thus requires lower levels of bio-safety precautions. The viruses are made by taking the backbone of another virus and replacing the surface proteins with those of SARS-CoV-2. These lab methods differ somewhat from the South African study reported yesterday, which used live virus (and didn’t have blood from people with 3 doses, but did have 2 doses + previous infection).
All of these differences can lead to the somewhat different results we see across studies.
So far the flurry of lab results suggests a significant hit in antibody effectiveness from Omicron, which was expected from its particular profile of mutations.
BUT– 3 doses of vaccine so far looks very good against Omicron. When you add other immune weapons such as T-cells that are more robust to variants, protection against severe disease should remain strong.
These studies will continue to come out fast and furious, so we’ll take a breather and wait more to accumulate. This way we can synthesize, which gives a better picture than individual studies.
Watch this space! #StaySafeStaySane
Those Nerdy Girls