Pfizer Inc and BioNTech SE said Thursday that they are testing the third dose of their COVID-19 vaccine to better understand the immune response against new strains of the virus.
They are also in talks with regulatory authorities about testing a revised vaccine to protect specifically against the new transmissible strain in South Africa and elsewhere, known as B .1.351, as a second arm of the same study.
The companies believe their current two-dose vaccine will work against the South African variant as well as one found in the UK and elsewhere. But the studies will allow vaccine manufacturers to prepare if and when more protection is needed, they said.
“The rate of mutations in the conventional virus is higher than expected,” Pfizer Chief Scientific Officer Mikael Dolsten said in an interview.
“It’s a reasonable likelihood that we would have a steady increase. And for strong vaccines, you may have to make a strain change every few years, but maybe not every year.”
In the first phase of the first arm of the study, as many as 144 people who received the vaccine 6 to 12 months ago in the initial Phase I safety trial will be given a third dose of 30 micrograms.
Assuming regulatory approval, a redesigned vaccine would also be tested, both as a dose increase in people who received the vaccine and in people who have not yet received the vaccine, Dolsten said.
The test would not attempt to measure the effectiveness of the vaccine like their major Phase III trial last year. Instead it would measure antibody response and examine whether blood from recipients can neutralize the new coronavirus variants, as well as the safety of a third dose.
Pfizer’s Dolsten said mRNA vaccines like Pfizer and BioNTech’s create a strong response. But the immune response may go away over time.
He believes that a third dose of their vaccine will produce a similar or better response than the second dose, which could be the next logical step for staying ahead of circulating changes.
“We believe our vaccine is strongly active against all sexes,” Dolsten said, noting that the companies “want to be prepared for all options and be data – driven – science – driven. “
Dolsten said the new test would likely be done mostly in the United States.
Pfizer and BioNTech are also said to plan to begin additional studies in five- to 11-year-olds over the next month or two, and in children under five later in 2021.
They are also planning studies to further evaluate the vaccine in people with immune systems.
Moderna Inc said Wednesday that it is also working with U.S. government scientists to study an experimental surge bullet targeting the variant first discovered in South Africa.