Pfizer Inc and BioNTech SE said on Thursday that they are testing a third dose of their COVID-19 vaccine to better understand the immune response against new variants of the virus.
They are also in talks with regulatory authorities about testing a modified vaccine to specifically protect against the new highly transmissible variant found 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, just like one found in the UK and elsewhere. But the studies will allow vaccine manufacturers to be prepared if and when more protection is needed, they said.
“The rate of mutations in the current virus is higher than expected,” said Pfizer’s scientific director, Mikael Dolsten, in an interview.
“It is a reasonable probability that we would end up with regular boosters. And for potent vaccines, you may need to change the strain every few years, but not necessarily every year.”
In the first stage of the first arm of the study, a third dose of 30 micrograms will be administered to up to 144 people who received the vaccine 6 to 12 months ago in the original Phase I safety trial.
Assuming regulatory approval, a redesigned vaccine would also be tested, both as a booster dose in people who have been vaccinated and in people who have not yet received the vaccine, said Dolsten.
The trial will not seek to measure the effectiveness of the vaccine as its major Phase III trial last year. Instead, it measures the antibody response and studies whether the blood from the receptors can neutralize the new variants of the coronavirus, as well as the safety of a third dose.
Dolsten of Pfizer said that mRNA vaccines like Pfizer and BioNTech create a potent response. But the immune response can decrease over time.
He believes that a third dose of the vaccine will create a response similar to or better than the second dose and may be the next logical step to stay ahead of circulating variants.
“We believe that our vaccine is strongly active against all strains,” said Dolsten, noting that companies “want to be prepared for all options and be guided by data – led by science”.
Dolsten said the new test is likely to be conducted predominantly in the United States.
Pfizer and BioNTech also said that they hoped to start additional studies in children between the ages of five and 11 in the coming months, and in children under five years later, in 2021.
They are also planning studies to better evaluate the vaccine in people with compromised immune systems.
Moderna Inc. said on Wednesday that it is also working with US government scientists to study an experimental booster injection that targets the variant first found in South Africa.