- AstraZeneca is planning to adapt its coronavirus vaccine to emerging variants that threaten to reduce the shot's potency "if required" by ongoing testing. Should a new version be needed, the British drugmaker on Thursday said it would take between six and nine months to ramp up to large-scale production.
- The announcement comes days after South Africa stopped rollout of AstraZeneca's vaccine following study results that showed the shot offered reduced protection against mild or moderate COVID-19 caused by the coronavirus variant prevalent in that country, called B.1.351.
- Other vaccine developers are adjusting, too. Moderna has begun work on a new booster shot designed to match the mutations observed in B.1.351. The biotech is also considering whether adding a third dose to its two-shot regimen would be sufficient to raise protection, as are partners Pfizer and BioNtech with their vaccine.
Viruses evolve over time as genetic copying errors accumulate. Some of the mutations can make a virus spread more easily among hosts, or cause more severe disease.
One coronavirus variant first identified in the U.K., called B.1.1.7, has been associated with increased transmissibility. Some of the mutations contained in B.1.351, meanwhile, involve the coronavirus' signature "spike" protein, potentially impairing antibodies' ability to bind and neutralize the virus.
Both of those variants have now been identified in the U.S., prompting some to forecast a wave of new infections that could reverse recent declines in new cases.
The vaccines now in clinical trials or already authorized for emergency use were designed to stimulate immunity to the original SARS-CoV-2 strain that emerged in Wuhan, China, just over a year ago. But B.1.351 has become the dominant strain in South Africa and could soon be so in the U.S., raising concerns over the potential for waning vaccine effectiveness.
So far, Moderna has tested its vaccine against a lab-developed "pseudovirus" that looks like B.1.351. When blood samples of vaccinated patients were exposed to the pseudovirus, lower levels of antibodies were produced than the company previously observed with the original virus. But Moderna expects the levels would still be sufficient for protection, although a third shot could be needed to keep up longer-term immunity.
Pfizer and BioNTech tested their vaccine against a pseudovirus that had a B.1.351 mutation thought to impair antibody binding, and found the antibody response was only slightly lower than against the original strain. Pfizer has said it will research a three-dose regimen, and may consider a variant-specific booster, too.
Alarm bells started ringing, however, with the disappointing news that AstraZeneca's shot, one of just a few approved globally, offered "minimal protection" against mild and moderate disease caused by B.1.351. The company on Thursday pointed out that the trial enrolled young and healthy patients, making it harder to determine whether vaccination was still protective against severe disease.
Differences in the vaccine technology used by AstraZeneca may make the U.K. company a bit slower to get a variant-specific booster out. Both Moderna's and Pfizer's vaccines use messenger RNA to spur an immune response — a technology that has been praised for its quick development cycle — while AstraZeneca and partner University of Oxford use a modified chimpanzee virus.
In a call with analysts Thursday, Menelas Pangalos, AstraZeneca's head of biopharmaceuticals research and development, described the company's efforts "a few weeks behind the mRNAs but not that far behind."
Getting to large-scale production will be enabled "by utilising existing clinical data and optimizing its established supply chain," the company said in its statement.