Pfizer and BioNTech surprised many sector watchers on July 27 when they announced that they would conduct a large-scale investigation into a vaccine for Covid-19. The surprise? The vaccine that would be tested in a trial of 30,000 patients was not something for which the companies presented data on July 1st.
The reason, the companies said, was that a second vaccine seems to generate a similar immune response, but less side effects. On Thursday, they posted the results of all 332 people who received vaccines, referred to as vaccines B1 as B2 – and indeed, B2 recipients experienced significantly fewer adverse events associated with the vaccine.
“Obviously, the better the vaccine is tolerated, the more I think it will stimulate public acceptance of a broad-based immunization,” said William Gruber, the former vice president of vaccine clinical research and development at Pfizer. ‘Both would have been great candidates. We were fortunate that B2 was actually satisfied with both a favorable immune profile and fewer responses. ”
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The study tested doses of each vaccine, ranging from 10 micrograms to 100 micrograms. The 30-microgram dose of B2 is advanced in clinical trials.
With the original vaccine, called BNT162b1, as B1 for short, patients between the ages of 18 and 55 had unusual events that were thought to be related to the vaccine 50% of the time at the 30 microgram dose. Those between the ages of 65 and 85 had relative adverse events 16.7% of the time.
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For the second vaccine, BNT162b2, as B2, patients between 18 and 55 had unusual events thought to be related to the vaccine 16.7% of the time, and no adverse effects thought to be related to the vaccine were reported in those between the ages of 65 and 85.
Both vaccines use mRNA – the genetic messenger that the body uses to make the DNA code in proteins – packaged in a fat capsule called a lipid nanoparticle, which allows it to enter cells. The mRNA instructs cells to make a protein, which then activates the immune system. For the B1 vaccine, the mRNA encoded the portion of an egg white on the SARS-CoV-2 virus that binds to a receptor on human cells to access them. The B2 vaccine makes up the whole of this protein, known as the spike protein.
By using the complete spike protein, the immune system can invent more ways to detect and attack the virus. Chemical modifications to the mRNA may also explain some of the difference. Although the same dose, by weight, was given to patients with each vaccine, the B2 vaccine would contain fewer particles because the full-length mRNA is heavier.
The close effects that were detected were mostly those that one would expect from a vaccine injection, including pain during injection, fever, chills, headache, and muscle or joint pain. No older adult receiving B2 reported redness or swelling at the injection site.
The mean level of antibodies to the virus in older adults was only 41% seen in younger participants. However, it was even higher than the level of antibodies seen in recovering patients, the authors said.
All patients in the B2 study were white and non-Hispanic, with more older women than older men participating. The younger patients were a median of 37 years old, while the older ones were a median of 69 years.
Pfizer has said that some data from its large study on vaccine B2 could come as early as October.
