A health worker in Mexico City prepares a Sputnik V dose. A new study in Mexico shows that non-mRNA vaccines like the Russian version can be as effective as Pfizer's vaccine if the patient has previously been exposed to the disease.
Luis Barron/Eyepix Group/Barcroft Media via Getty ImagesMore than 20 COVID vaccines are in use around the world, each one based on the ancestral coronaviruses that surfaced in China over two years ago. The best protection against severe disease is believed to be offered by the mRNA vaccines.
It has been clear for a while that none of them are as good as the vaccine that dominates the U.S. landscape.
Pfizer and Moderna shots are referred to in New York.
A preprint study shows that other vaccines can be as effective as the one given to people with a previous SARs-CoV-2 infection.
Theodora Hatziiouannou, a virologist at The Rockefeller University in New York who helped lead the study, says that for these individuals, it doesn't matter which vaccine they get.
Scientists collected blood samples from over 200 fully-immunized people in Mexico, where five types of COVID vaccines have been deployed so far. The researchers had records of which type of shot each person had, and half of them were infectious before they were given a vaccine.
The team measured how well immune cells and the molecule they produce in the blood could bind to the parts of the SARS-CoV-2 virus. The spike proteins from the CoV-2 are similar to studs on a tire. When the immune components are able to block the proteins, the virus is unable to enter a cell and can't replicate.
The researchers tested the immune response to spike proteins from the ancestral coronaviruses as well as newer ones. When the study began, the newer omicron BA.2 variant was not evaluated.
The team zeroed in on two of the immune system's key components to compare how well the vaccines worked.
They provide a frontline defense against spikes from their human cell target.
Second are B cells that can be used for long-term reinforcements. These cells can rapidly generate new and even better antibodies against the virus after the front-line neutralizing antibodies have waned.
Two sets of results were revealed by analyzing the blood samples. The best anti-viral responses came from people who hadn't yet been exposed to SARs-CoV-2. The strength of those responses waned a bit more with each variant of the virus. Although the vaccines could not prevent infections by omicron, they could give added protection from severe disease. T cells weren't measured in the study.
In people who had been exposed to SARs-CoV-2 and had beenvaccinated, the outcome was completely different: All the vaccines provided a major immunological boost against re-infection, and the differences between the mRNA shots and the other ones blur.
Four of the five vaccines produced similar immune reactions. Pfizer's shot was one of the shots included in this group, as was the Sputnik V shot made by the Gamaleya Research Institute of Epidemiology and Microbiology in Russia. CoronaVac, a vaccine made by Sinovac Biotech in China, was the worst performer.
The vaccines work in different ways. The lab-created molecule that teaches cells to recognize and respond to future infections is created by Pfizer. The Sputnik V and Cansino shots deliver genetic instructions for responding to the spike proteins of the cold virus but not the real one.
The Sinovac vaccine is made of particles that have been killed.
Paul Bieniasz, a researcher at The Rockefeller University and a corresponding author on the paper, says Pfizer's vaccine is the best one for un-infected people because it exposes the immune system to more spike protein than the other vaccines.
Why do the different vaccines perform the same? Bieniasz says the explanation is how memory B cells prepare for a future attack. The cells go through a training process called affinity maturation that teaches them how to make better antibodies against the variant that they were first exposed to. Bieniasz says that after a previously infectious person isvaccinated, trained B cells spring into action.
A newly published Israeli study supports the idea that a vaccine protects against future infections after a case of COVID. After recovering from COVID, unvaccinated individuals who were given a Pfizer vaccine had a lower risk of reinfection.
The Rockefeller paper tells you that the vaccine you use is inconsequential, and the Israeli paper tells you that the vaccine you use has real-world benefits.
Moore says that a single vaccine dose was sufficient to confer benefit in the Israeli study, which suggests that the standard two-dose regime is not necessary for people who have already been exposed. Moore says that Halving the two-shot regimen would save a lot of doses.
Evidence that non-mRNA vaccines are powerfully protective for the vast numbers of people with prior infections is welcome news, especially in countries where those shots have been widely adopted. The other vaccines have a lot to do with how they accumulate immunity.
Charlie is a science writer based in Maine. His work has appeared in a number of publications.
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