Slowly but surely, more and more clear about the possible duration of protection of the approved corona vaccines. This week it became known that Pfizer and Moderna vaccines could possibly provide years of protection against the coronavirus. And the first results of an Oxford University study show that antibodies remain elevated with AstraZeneca for at least one year after the first dose.
Thats good news, say Ben van der Zeijst, Emeritus Professor of Vaccines, and immunologist Dimitri Diavatopoulos of Radboudumc, Nijmegen. And also has an effect on vaccination in the Netherlands: repeated punctures can only be needed later.
“It all looks very good,” says Van der Zeijst, also former director of the Dutch Vaccine Institute and former head of Vaccines at RIVM. “At first, we were afraid that a repeat shot would have to be planned after half a year, but everything suggests that it is not necessary.”
What are antibodies?
In order to understand exactly what the research results mean, first we need to consider what antibodies are.
If you are vaccinated with a corona vaccine, your immune system responds to it. It produces antibodies – which protect against contamination – and t-cells (immune cells) that reduce the severity of the disease in case of infection.
Antibodies form in the mucous membranes of the respiratory tract and act literally like a shield, explains Diavatopoulos. “The antibodies catch the virus and prevent it from attaching to your airways and therefore cannot multiply.” The chances of getting very sick or death from corona with antibodies in your body is negligible.
How a vaccine works is also explained in this video:
After vaccination with the approved corona vaccines, everyone has a high number of antibodies in their body. These may decrease at some point, which means you become more susceptible to coronavirus infection again.
So you want the number of antibodies in your body to stay as high as possible. The study on the mRNA vaccines Pfizer and Moderna shows that the antibodies you get from the vaccine are ripening, says Diavatopoulos. “The antibody formation process continues to work. That probably means that the antibodys defenses arent gone soon.” The research on vector vaccine AstraZeneca also shows that these antibodies remain high.
This may mean that no “booster vaccinations”, a kind of repeat prick, will be required in the coming period. But how long that will last is hard to estimate. According to the research, this may take years in the MRNA vaccines, and AstraZeneca talks about a year. No research results have yet been known about the Janssen vaccine, but chances are that it will show the same results as vector vaccine colleague AstraZeneca, says Van der Zeijst.
But the antibodies are not the only relevant cells to look at, says Van der Zeijst. “If the antibodies go away, it doesnt mean youre completely unprotected against the coronavirus. You also have memory cells called “memory b cells” that can create antibodies when your body comes back into contact with the virus.”
They may stay in your body for a period of ten years, says the emeritus professor. So those memory cells can protect you, but with a delay. “Antibodies protect right away, memory cells need a few days to create new antibodies.”
Still, it remains an estimate when a repeat prick is going to be needed – if this ever happens at all. “We dont know exactly how many antibodies are needed to protect against infection or serious illness. So you dont have a threshold you can do research on. We know that the number of antibodies people have now is enough, but at some point it ends. When is it too little? We dont know that yet,” says Diavatopoulos.
Difference with vector vaccines
However, vector vaccines Janssen and AstraZeneca are more likely to require a repeat puncture than the MRNA vaccines Pfizer and Moderna, both experts say. The vector vaccines produce fewer antibodies. That doesnt mean that these vaccines work less well.
Diavatopoulos: “The vector vaccines have more powerful immune cells, called t-cells, which make you less ill with an infection. Because these vaccines produce fewer antibodies, they are a little less good at protecting against contamination, but if you get infected, they can protect you well. They may be better at removing the virus than in preventing it.”
Both experts think it will certainly take some time for a repeat prick to be needed. “The vaccination will be more and more likeother infectious disease vaccination campaigns, in which it may only be necessary to vaccinate people with weak immune systems again,” says Diavatopoulos. Van der Zeijst expects it to take at least two to three years for the first repeat puncture to be needed. “And maybe its not necessary at all.”
However, these scenarios depend on how the virus mutates and whether the vaccines protect against new virus variants. “If the vaccines are found to be less effective against a new variant, chances are that a repeat prick will be required. A special repeat print that protects against all these variants. But that wont be necessary in the coming months, I think,” says Van der Zeijst.