Get the COVID-19 vaccines while they still work. New findings from Novavax and Johnson & Johnson and Novavax—two companies with candidates in late-stage clinical trials—show strong protection against the original strain of the coronavirus. But these drugs may not be able to maintain herd immunity and protect communities in the long run.

Early estimates suggested COVID-19 vaccines need to be about 75% effective against infection to establish herd immunity, but Dr. Anthony Fauci of the National Institute of Allergy and Infectious Diseases said in December that the mark might be closer to 90%. Overall effectiveness for both vaccine candidates fell well below this level when facing the coronavirus variant from South Africa named B.1.351.

“By our PCR [testing], it appears over 90% of the cases [in South Africa] were attributable to the escape variant, and that was, of course, aligning with what we saw in the epidemiology,” Dr. Gregory M. Glenn, President of Research and Development at Novavax, said during a conference call on Thursday. He also added that prior infection with the original strain might not generate immunity to the South African variant, parallelling results from recent studies.

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The Maryland-based Novavax presented phase 3 results from South Africa and the U.K, where a different variant is spreading rapidly and overwhelming hospitals. The company’s two-dose vaccine mounted an excellent defense against the original strain of the coronavirus and the U.K. variant, shielding 90% of British takers from mild, moderate, or severe disease.

“With today’s results from our U.K. Phase 3 and South Africa Phase 2b clinical trials, we have now reported data on our COVID-19 vaccine from Phase 1, 2 and 3 trials involving over 20,000 participants,” Stanley C. Erck, Novavax President and CEO said in a statement. “In addition, our PREVENT-19 US and Mexico clinical trial has randomized over 16,000 participants toward our enrollment goal of 30,000.”

But in South Africa, the efficacy dropped to 60% due to the rapid spread of the B.1.351 variant, which vibes with earlier reporting that this mutant is more likely to escape our immunity. The protection shrank by another 10% when they included HIV patients, who tend to be immunocompromised.

In response to the Novavax disclosure, Natalie Dean, an epidemiologist at the University of Florida, tweeted enthusiasm over the U.K. trial, but said: "we cannot assume that vaccines are equally effective against all variants."

The long-awaited results from Johnson & Johnson arrived Friday morning. Mayor Bill de Blasio and Governor Andrew Cuomo have recently voiced excitement over this candidate, given it requires only one shot. It can reach more people with fewer doses than the authorized options from Pfizer-BioNTech and Moderna.

Their interim analysis reported 72% efficacy in the U.S., but the overall protection against moderate and severe COVID-19 dropped to 66% when they included results from other countries. Why? Because researchers saw 66% efficacy in Latin America and 57% in South Africa.

On a positive note, the Johnson & Johnson candidate guarded more than four out of five people from severe COVID-19. No deaths or hospitalization were reported among those immunized. Their trial involved 43,783 global participants split across placebo takers and vaccine recipients. The Johnson & Johnson vaccine is produced by its subsidiary Janssen.

Assuming these vaccines block the coronavirus's spread at a similar rate as they stop its disease, these updates bode poorly on their abilities to establish herd immunity. Meanwhile, reaching herd immunity by the summer or autumn was already looking like an uphill battle given the slow nature of the vaccine rollout.

The mutant strains, especially the concerning ones from South Africa and Brazil, place extra urgency on getting doses into people’s arms before the virus spread broadly or make our life-saving drugs ineffective. New Jersey reported the first U.S. death connected to the UK variant, while South Carolina health officials recorded the country’s first cases of the South African variant on Thursday.

Glenn said Novavax is already preparing to update its vaccine formula in a bid to stop the new mutants. Both Pfizer and Moderna are doing the same. Johnson & Johnson launched a second trial in December that added a booster shot to their regimen to increase their overall efficacy.

Gothamist has contacted Johnson & Johnson and Novavax for comment.