Pfizer announced Wednesday its vaccine booster shot increases antibody protection against COVID-19 by 25-times.
That good news is coupled with results from local researcher Dr. Thomas McDade who is testing blood samples against the omicron variant.
He said it’s important to discuss antibodies but it’s equally critical to focus on cellular immunity which lasts longer than the initial vaccine antibody boost.
“Covid infections and vaccines boost short term antibodies,” he said. “Those antibodies trigger long term immune memory in the form of B and T-cells.”
McDade is an anthropologist at Northwestern Medicine.
“The immune system has two main arms that are really important for protecting us against SARS,” he said.
Breakthrough infection shows the process in action. As vaccinated people whose antibodies wane, making it easier to test positive for COVID-19 — but T and B-cells help them not get as sick.
“So that’s why we are saying there are breakthrough infections, but we are not seeing a dramatic rise in hospitalizations and deaths because cellular immune defenses don’t go down as much overtime,” McDade said. “We are developing new test of cellular immunity that we hope we can roll out in the community to facilitate our understanding of who is immune, who might need to get boosted, how the vaccine is working in the general population.”
Until that test is ready, McDade and his team are analyzing immunity in blood samples of Covid survivors, vaccinated and boosted patients.
“What we are seeing with Omicron is similar to the story with Delta over the summer, the variant has changed a bit which means that the vaccine that we all received which was generated against the original version of the virus isn’t quite as effective, but it is still very effective,” he said. “Especially with our cellular immune defenses.”
A blood sample from a person before and after vaccination had a pattern similar to the blood of someone who recovered from Covid then got the vaccine. After the first dose there was a small response, it was a little better for the previously infected. After the second shot antibodies shot up, but they wane over the next six months.
“Over the summer antibodies start to come down and we are back basically where we were after the first vaccine dose,” McDade said of the samples. “Once you have a booster dose your antibodies go up to over 100. So that is four times higher than where you were after vaccination dose two. And it’s 25 times higher than where you were the week before. Because your antibodies have gone down overtime.”
the original vaccine was not designed to target the hundreds of mutations in omicron but McDade said, “You have strength in numbers here even if the fit isn’t exactly right. … If we increase our antibodies overall, even if they are not a perfect match for omicron, they should be effective at preventing infection.”
Keeping up with a rapidly mutating virus is like focusing on the flu, only faster.
“We all have some experience with it, particularly through childhood and we carry that forward. And that’s where we will get to eventually with Covid-19,” McDade said. “The more people who can get vaccinated globally, the less virus will be in circulation, the fewer opportunities it will have to evolve a new variant that escapes our immune defenses and we will all be in better shape.”
Just like it is not realistic to think we will never get a cold or the flu, early vaccine success may have unrealistically raised expectation we would not get Covid. Experts say it is likely here to stay.