Moderna, Pfizer test vaccine strategies against new variants

Vaccine makers Pfizer and Moderna are trying to get out ahead of some of the new coronavirus variants that are causing concern around the world.

Although there's no evidence people immunized with either vaccine have less protection against the variants, both companies said they have started looking at ways to account for evolving mutations.

Especially worrying is the B.1.351 variant first seen in South Africa. It carries a mutation that helps it elude the body's immune response to infection. The B.1.1.7 variant first seen in the UK is also causing concern, as its mutations appear to make it more transmissible, so it spreads better, and it may also cause more severe disease.

Researchers are also finding variants across the US that have developed mutations that help them evade the immune system.

Pfizer and its partner BioNTech said Thursday they have begun to test how well adding a third dose of their authorized vaccine might protect against new variants.

he study will look at the safety and immune response of a booster dose in up to 144 participants from the earlier Phase 1 trial in the US, including a subset of older adults up to age 85. It will also involve testing how well their antibodies are able to neutralize "strains of interest" in the lab, the companies said.

Volunteers would receive a third dose between 6 to 12 months after their earlier two doses. The dosage would be identical to what's currently authorized: 30 micrograms.

"This booster study is critical to understanding the safety of a third dose and efficacy against circulating strains," Pfizer CEO Dr. Albert Bourla said in a statement.

Separately, Pfizer and BioNTech are also "in ongoing discussions with regulatory authorities" about potentially testing a vaccine modified to protect against concerning variants in a Phase 1/2 study.

However, Bourla noted the companies haven't yet seen compelling evidence that variants are resistant to its vaccine, though they are taking steps to be prepared.

Moderna said late Wednesday it has produced an updated version of its Covid-19 vaccine to help it combat the B.1.351 variant first seen in South Africa. Initial doses have been shipped to the National Institutes of Health for a clinical study.

The new vaccine, called mRNA-1273.351, will be evaluated as a booster shot for people who have already been vaccinated against coronavirus and as a primary vaccine for people who haven't had coronavirus and have yet to be vaccinated.