In recent months, several variants of SARS-CoV-2, the virus that causes COVID-19, have emerged. The most notable of these are B.1.1.7, first identified in the United Kingdom; B.1.351, first identified in South Africa; and P.1, first identified in Brazil. To be considered a variant, a virus must have sufficient mutations to change a portion of its genetic code. The B.1.1.7 variant has 17 mutations, the B.1.351 variant has 10 mutations, and the P.1 variant has three mutations. Findings from three recent studies indicate that vaccines and boosters using mRNA technology or recombinant technology are effective against the variants.

mRNA-based vaccines contain the genetic instructions for synthesis of a single viral protein that, when injected into the body, stimulates the immune system to make antibodies against a spike protein located on the SARS-CoV-2 surface. The use of mRNA vaccine technology allows rapid scaling of vaccine production and facilitates modification if the virus mutates significantly. Two mRNA vaccines (Pfizer-BioNTech and Moderna) are currently authorized for use in the United States.

Recombinant vaccine technology inserts the genetic information for the spike protein into insect cells, which are then harvested, purified, and housed in nanoparticles. The Novavax recombinant vaccine has been tested in trials in the United States, United Kingdom, Mexico, and South Africa.

The first of the studies assessed effectiveness of the Pfizer-BioNTech vaccine against the B.1.1.7 variant. The study was conducted in Israel, where 95 percent of all COVID-19 cases were caused by the B.1.1.7 variant. The authors of the study found that two doses of Pfizer-BioNTech vaccine were 97 percent effective against COVID-19 (including those caused by the B.1.1.7 variant) in vaccine recipients aged 16 to 85 years.

The second study was a phase 2 trial that assessed three candidate mRNA vaccines from Moderna: a booster against B.1.351; a combination booster containing a 50-50 mix of the original vaccine and the B.1.351 vaccine; and a booster containing a lower dose of the original vaccine. Vaccination with the B.1.351 booster or the 50-50 mix of the B.1.351 vaccine and the original vaccine increased antibody titers against both the B.1.351 and P.1 variants.

A third study looked at the effectiveness of the Novavax vaccine against the B.1.351 variant among people living in South Africa, where the variant first emerged. The vaccine was tested among HIV-negative and HIV-positive participants. It was 60 percent effective against mild, moderate, and severe COVID-19 illness in HIV-negative participants and 50 percent effective in HIV-positive participants.

These findings indicate that three commonly used vaccines are highly effective against emerging SARS-CoV-2 variants in adults. Ongoing and future trials will assess their efficacy and safety in other populations.

• Link to Pfizer study.00947-8/fulltext)

• Link to Moderna press release.

• Link to Novavax study.