A second experimental coronavirus vaccine tested by Pfizer Inc and its German partner BioNTech SE has shown promising results.
Both companies claim that their second injection produced as many antibodies in the volunteers as their first injection, but had far fewer side effects.
Results published in the New England Journal of Medicine on Wednesday showed that the first stroke was more likely to cause injection site pain, fever, fatigue and chills compared to the second stroke.
It was also better tolerated by older participants, who are much less likely for vaccines to induce immune responses due to their weakened immune systems.
The results come on the heels of Pfizer’s announcement of its intention to recruit participants as young as 12 in its large, late-stage COVID-19 vaccine trial to understand how vaccination works in a group of younger age.
The coronavirus vaccines tested by Pfizer Inc and BioNTech SE use a genetic code with B1 encoding part of the protein that the virus uses to enter and infect human cells and B2 encoding all proteins. Pictured: Pfizer Inc. headquarters in New York City, July 22
After receiving B1, 77% of 18 to 55 year olds had reactions compared to 75% after B2, although there were fewer reports of redness and swelling
About 80% of adults aged 65 to 85 reported mild to moderate reactions after B1 compared to 55% for B2, which did not cause any 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 into recognizing the coronavirus and attacking it if a person is infected.
In the first vaccine, BNT162b1 (B1), mRNA encodes part of the protein that the virus uses to enter and infect human cells.
For the second vaccine, BNT162b2 (B2), the mRNA encodes the entire protein, called the spike protein
In the randomized, placebo-controlled trial, researchers tested a low dose of 10 micrograms (µg), a medium dose of 20 µg, and a high dose of 30 µg.
A total of 195 participants were divided into groups of 15 each in which they received either two doses 21 days apart between 10 µg, 20 µg or 30 µg, or a placebo.
About 77% of 18 to 55 year olds and 80% of 65 to 85 year old adults who received B1 reported mild to moderate reactions.
The most common side effect was pain at the injection site within seven days of inoculation.
Antibody levels in the older group were lower than in the younger group, but still higher than those seen in cured patients (above)
It comes as Pfizer announced that it is looking to enroll participants as young as 12 for its trial. Pictured: First patient enrolled in Pfizer’s COVID-19 coronavirus vaccine clinical trial at the University of Maryland, Baltimore School of Medicine, receives an injection, May 4
A few participants also reported redness and swelling, especially after the 30 µg dose.
In comparison, 75% of 18 to 55 year olds and 55% of 65 to 85 year olds reported reactions to B2.
A few members of the younger group reported redness or swelling after dose 1 of B2, but none did after dose 2.
No member of the older group experienced any redness or swelling after either dose – just pain at the injection site.
In addition, the authors note that the B1 vaccine was more likely to induce side effects such as fever, fatigue and chills than B2.
Systemic events (fatigue, headache, chills, muscle pain and joint paint) have been reported in a small number of [B2], but no serious systemic events have been reported by older recipients of this vaccine candidate, ”the authors wrote.
No volunteer in any group has experienced events qualified as “grade 4”, often fatal or requiring hospitalization.
The team says antibody levels were similar in patients who received the B1 or B2 vaccine.
Levels of IgG antibodies, which bind to the virus, and neutralizing antibodies were increased by the second dose in younger participants, but less in older participants.
However, the levels were even higher than those seen in cured patients, according to the study.
Last month, Pfizer announced it was expanding its trial to include up to 44,000 participants, an increase from 30,000, and include those with HIV, hepatitis C and hepatitis B.
On Monday, nearly 38,000 people signed up at trial sites in four countries, including the United States.
The results also come as several drugmakers have suspended their own late-stage coronavirus vaccine trials
Johnson & Johnson suspended its trial on Monday due to an “unexplained illness” in a participant, details of which are unclear.
Meanwhile, the U.S. branch of the University of Oxford and AstraZeneca vaccine trial has been on hold since last month, although testing has resumed at all other sites.
Additionally, Eli Lilly announced on Wednesday that he would continue testing his anti-coronavirus drugs after he suspended at least one trial due to “potential safety concerns.”