Enlarge / Vials in front of the AstraZeneca British biopharmaceutical company logo are seen in this creative photo taken on 18 November 2020. (credit: Getty| NurPhoto )

Dismal preliminary data on AstraZeneca’s COVID-19 vaccine in South Africa—where the B.1.351/ 501Y.V2 coronavirus variant is spreading widely—lead the government there to rethink its vaccination rollout and raised further international concern about the variant .

But the small study has so many limitations and caveats, experts caution that drawing any conclusions from it is difficult.

The study, which has not been published or peer-reviewed but presented in a press conference Sunday , began in June and enrolled only around 2,000 participants, about half of which received a placebo. Early in the study—before B.1.351 emerged—the vaccine appeared over 70 percent effective at preventing mild-to-moderate cases of COVID-19. That is largely in line with the conclusion of an international Phase III trial released by AstraZeneca and vaccine co-developer Oxford University, which showed mixed results for the replication-deficient adenovirus-based vaccine but an overall efficacy of around 70 percent .

Enlarge (credit: CDC.gov )

As the world races to get vaccines into arms, one of the most concerning coronavirus variants appears to be getting a little more concerning.

Researchers in the UK have detected at least 15 cases of B.1.1.7 variants carrying an additional mutation: E484K—a mutation already seen in other concerning variants , and one that may make current vaccines less effective at preventing infection. The B.1.1.7 variant, first identified in the United Kingdom, is already known to spread more easily among people than earlier strains of the pandemic coronavirus SARS-CoV-2. And according to some preliminary evidence, it may cause more severe disease.

So far, B.1.1.7 variants carrying E484K appear rare. On Monday, Public Health England reported in a technical briefing that it had detected E484K in just 11 B.1.1.7 variants among more than 200,000 viruses examined. For now, it’s unclear if the augmented mutants will take off and become dominant in the population or fizzle out. It’s also not entirely clear what the addition of E484K means for B.1.1.7 in people. Preliminary laboratory experiments suggest the mutation alone and its presence in B.1.1.7 specifically may help the virus evade immune responses. But more studies and clinical data are necessary to understand the full effect of the new addition.

Enlarge / Coronaviruses (credit: Getty | BSIP )

Ever since the novel coronavirus, SARS-CoV-2, began jumping from human to human, it’s been mutating. The molecular machinery the virus uses to read and make copies of its genetic code isn’t great at proofreading; minor typos made in the copying process can go uncorrected. Each time the virus lands in a new human victim, it infects a cell and makes an army of clones, some carrying genetic errors. Those error-bearing clones then continue on, infecting more cells, more people. Each cycle, each infection offers more opportunity for errors. And, over time, those errors, those mutations, accumulate.

Some of these changes are meaningless. Some are lost in the frenetic viral manufacturing. But some become permanent fixtures, passed on from virus to virus, human to human. Maybe it happens by chance; maybe it’s because the change helps the virus survive in some small way. But in aggregate, viral strains carrying one notable mutation can start carrying others. Collections of notable mutations start popping up in viral lineages, and sometimes they seem to have an edge over their relatives. That’s when these distinct viruses—these variants—get concerning.

Scientists around the world have been closely tracking mutations and variants since the pandemic began, watching some rise and fall without much ado. But in recent months, they have become disquieted by at least three variants. These variants of concern, or VOCs, have raised critical questions—and alarm—over whether they can spread more easily than previous viral varieties, whether they can evade therapies and vaccines, or even whether they’re deadlier.