A second experimental coronavirus vaccine tested by Pfizer Inc and its German partner BioNTech SE showed promising results.
The two companies say their second batch produced as many antibodies in volunteers as their first batch, but had far fewer side effects.
The results, published Wednesday in the New England Journal of Medicine, showed that the first shot was more likely to cause injection site pain, fever, fatigue, and chills compared to the second shot.
It was also tolerated better by older participants, in whom vaccines were much less likely to trigger immune responses due to their weakened immune systems.
The results follow on from Pfizer's announcement to include participants 12 years and older in its large, late-stage COVID-19 vaccine trial to understand how immunization works in a younger age group.
The coronavirus vaccines tested by Pfizer Inc and BioNTech SE use genetic code with B1 coding for part of the protein that the virus uses to enter and infect human cells and B2 coding for all of the protein. Pictured: Pfizer Inc headquarters in New York City, July 22nd
After receiving B1, 77% of 18-55 year olds experienced reactions compared to 75% after B2, although fewer reports of redness and swelling were reported
About 80% of adults aged 65 to 85 years reported mild to moderate reactions according to B1 compared to 55% in B2, which caused no redness or swelling after either dose
Each Pfizer and BioNTech vaccine candidate uses part of the pathogen's genetic code, called mRNA, to trick the body to recognize the coronavirus and attack it when a person becomes infected.
In the first vaccine, BNT162b1 (B1), the mRNA codes for part of the protein that the virus uses to enter and infect human cells.
For the second vaccine, BNT162b2 (B2), the mRNA codes for the entire protein, called the spike protein
In the randomized, placebo-controlled study, the researchers tested a low dose at 10 micrograms (µg), a medium dose at 20 µg, and a high dose at 30 µg.
A total of 195 participants were divided into groups of 15 participants each, in which they received either two doses of 10 µg, 20 µg or 30 µg or a placebo, 21 days apart.
About 77 percent of 18 to 55 year olds and 80 percent of adults 65 to 85 years old who received B1 reported mild to moderate reactions.
The most common side effect was pain at the injection site within seven days of inoculation.
The antibody levels in the older group were lower than in the younger group, but still higher than in the recovered patients (above).
It comes when Pfizer announced that participants 12 years and older would be enrolled in the study. Pictured: The first patient enrolled in Pfizer's COVID-19 coronavirus vaccine clinical trial at the University of Maryland Medical School in Baltimore receives an injection on May 4th
Some participants also reported redness and swelling, especially after the 30 µg dose.
For comparison: 75 percent of 18 to 55 year olds and 55 percent of 65 to 85 year olds reported reactions to B2.
Some in the younger group reported redness or swelling after dose 1 of B2, but none after dose 2.
None of the older groups had redness or swelling after either dose – just pain at the injection site.
In addition, the authors note that the B1 vaccine is more likely to cause side effects such as fever, fatigue, and chills than B2.
"Systemic events (fatigue, headache, chills, muscle pain, and joint color) have been reported in a small number of younger recipients of (B2), but older recipients of this vaccine candidate did not report any serious systemic events," the authors wrote.
None of the volunteers in a group experienced events classified as "Grade 4" which are often life threatening or requiring hospitalization.
The team says antibody levels were similar in patients who received either the B1 or B2 vaccine.
The levels of IgG antibodies that bind to the virus and neutralizing antibodies were increased by the second dose in younger participants, but less in older participants.
However, according to the study, the values were still higher than those of recovered patients.
Last month, Pfizer announced it would expand the study to up to 44,000 participants, an increase of 30,000 including HIV, hepatitis C and hepatitis B.
As of Monday, nearly 38,000 people had enrolled at test sites in four countries, including the U.S.
The results also come when several drug manufacturers paused their own late-stage coronavirus vaccine trials
Johnson & Johnson dropped out on Monday for "unexplained illness" in a participant whose details are unclear.
Meanwhile, the US portion of the study for Oxford University and AstraZeneca's vaccine has been on hold since last month, although testing has resumed at all other sites.
In addition, Eli Lilly announced on Wednesday that it would continue testing its coronavirus antibody drugs after at least one study was suspended due to "potential safety concerns".
(tagsToTranslate) Dailymail (t) Health (t) Coronavirus