The coronavirus vaccine developed by Moderna triggers an immune response that protected against two variants of the virus first detected in Britain and South Africa in laboratory tests, the company said Monday.
But the reassuring news that vaccine-elicited antibodies remained effective against concerning new variants was tempered by an ominous finding. Those antibodies were less efficient at neutralizing the South African variant in a laboratory dish - a sixfold reduction in response foreshadowed by a small, but mounting body of evidence that has trickled out recently showing that the variant may have the potential to elude parts of the immune response.
As a precaution, Moderna announced it will launch two new studies. The company will test adding a third shot of its current vaccine to boost its two-dose regimen. Scientists have already designed an all-new vaccine specific to the South African variant that could be used as a booster to prime the immune system to the new strain, and plan to test it in the coming months.
“The virus is changing its stripes, and we will change to make sure we can beat the virus where it’s going,” Stephen Hoge, president of Moderna, said in an interview. “The unknown is would we feel it’s necessary to do that, would public health officials want this at that point or would they still be comfortable? What we’re trying to do is create an option.”
The detection of both variants late last year triggered immediate concern, first because of evidence they were spreading far more easily. But many of the mutations in each variant - eight of those found in the British variant and 10 of those in the South African variant - drew special concern because they sit in the spiky proteins that dot the outside of the coronavirus and have been the key target for vaccines and therapeutics. That raised the specter that the current generation of vaccines might be rendered obsolete before they have even been rolled out.
The company’s announcement puts some of those fears to rest, suggesting the vaccines will still work against both variants.
Antibody-containing blood serum taken from people and monkeys who received the vaccine was just as effective at blocking the British variant as the original strain of virus in the study, and remained above the threshold for efficacy for the South African variant, despite the diminution in effectiveness. The work has been submitted to a preprint server, but has not been peer-reviewed and was not available for review before publication.
The company reported a sixfold decrease in the ability of antibodies to block the virus - a drop that Hoge said was concerning but not alarming - underscoring the need to remain vigilant.
The report comes after similar news from Pfizer-BioNTech, which released data last week, also not yet peer-reviewed, showing that antibody-rich blood serum samples from 16 vaccinated people showed that vaccine was equally as effective at blocking the British variant as it was against the original version of the virus that took hold in Wuhan, China, a year ago. That publication did not address the South African variant, which has been of most concern and shares many mutations with a concerning variant detected in Brazil.
Laboratories across the world have been scrambling to study whether vaccines and treatments, particularly monoclonal antibodies, are likely to be as effective against the new variants. So far, such tests have mainly relied on one part of the multifaceted immune response and found evidence the vaccines are likely to be effective - but have underscored the need to track changes in the virus and prepare for the eventuality that, like flu shots, a coronavirus vaccine might need to be updated and administered on a regular basis.