More than 33 million Americans have been fully vaccinated against COVID-19 – more than the number of cases reported in the United States during the pandemic. But the proliferation of harmful variants, some of which may partly escape vaccines, means that we are not out of danger.
New research suggests that the shots from Moderna and Pfizer are significantly less effective against the variant first found in South Africa, called B.1.351. That study used blood samples from vaccinated people to compare antibody responses to the original virus and to variant B.1.351. Those who received the injections had far less antibodies capable of neutralizing B.1.351.
The study authors said that both vaccines were also likely to be less effective against P.1, a variant found for the first time in Brazil.
The chart below summarizes what we know so far about how five vaccines work well to protect people from three of the most worrying variants of the coronavirus.
3 variants, 3 stories
Numerous versions of the coronavirus circulate around the world, each separated by a small number of genetic mutations.
Since a series of mutations makes a given strain better at infecting people, more lethal or better able to avoid the antibodies generated by a previous vaccination or infection, geneticists label it as a worrying variant.
There are three of them: B.1.1.7, the variant initially detected in the United Kingdom in September; P.1, which was discovered in December; and B.1.351, which was detected in samples from South Africa dating from October.
A healthcare professional removing a nasal swab from a patient to test COVID-19 in Cape Town, South Africa.
Nardus Engelbrecht / AP Pictures
They share a mutation that affects the form of the virus’s spike protein, which is used to invade cells. This may be why these variants are more transferable.
Studies have found that variant B.1.1.7 – which has been reported in 94 countries, including the United States – is 50% to 70% more contagious than its viral predecessors. Recent evidence suggests that people infected with this variant may face a higher risk of death than those who contract other strains.
Variant B.1.351 has been reported in 48 countries and 23 states in the USA. But studies have not found it to be more lethal than the original virus.
The same goes for the P.1 variant, which a March study suggested was 40% to 120% more transmissible than previous versions of the virus. P.1 has been detected in 26 countries and 10 states in the USA.
A nurse showing a COVID-19 vaccine produced by the Chinese company Sinovac.
SILVIO AVILA / AFP via Getty Images
Research suggests that existing vaccines work to protect people from B.1.1.7, but are less effective against B.1.351 and P.1. This is probably because these two variants share a mutation that can prevent antibodies generated in response to the original virus from recognizing them.
This genetic adjustment is mainly lacking in variant B.1.1.7, although researchers in the United Kingdom have found 11 cases of B.1.1.7 with this mutation in a set of more than 200,000 samples.
B.1.351 and P.1 also have a mutation that can help the virus to bind more strongly to cells.
What these variants mean to you
Both Pfizer and Moderna said in January that they planned to develop and test reinforcement shots to address variant B.1.351. This means that vaccinated people may need a follow-up injection. Until then, people who have been vaccinated or received COVID-19 previously may still be at risk of infection with variants B.1.351 and P.1.
A nurse receives the COVID-19 vaccine in Galveston, Texas, on December 15.
Mark Felix / AFP via Getty Images
However, vaccines are likely to still provide some degree of protection against these variants, even if they are less effective.
“The more vaccines we can get into people’s arms, the fewer general infections,” said Kristian Andersen, an immunologist at the Scripps Research Institute in California, tweeted in January. That includes infections with variants B.1.351 and P.1, he added.
Furthermore, variants jump between hosts in the same way as the original virus, so social detachment and the use of personal protective equipment should still help prevent its spread. That is why these mitigation measures remain critical – especially considering that if you are exposed to a more transmissible variant, you are more likely to be infected.
“We are going to put our genomic surveillance in place, better masks, more masks, tests and screening much more widespread – and avoid meetings and crowded environments,” Andersen wrote. “Combine that with accelerated vaccine delivery and an accelerated plan for updated reinforcements.”
Dr. Catherine Schuster-Bruce contributed to the account of this story.