Safety concerns with J&J's COVID-19 vaccine present a big opportunity for Pfizer, Moderna: analyst

coronavirus vaccine
Johnson & Johnson has distributed approximately 7 million COVID-19 vaccine doses in the U.S., but even with the shot paused, experts believe more safety data will be available next week, when many more have passed through a two-week window when blood clot events have occurred.(nevodka/iStock/Getty Images Plus/Getty Images)

Developing a single-shot COVID-19 vaccine with less stringent cold-storage requirements seemingly gave Johnson & Johnson a major advantage over mRNA coronavirus vaccine producers. As a result, its rollout was anxiously awaited.

But with a pause of the J&J shot in the United States and Europe as officials investigate rare and severe blood clots, that edge is quickly diminishing.

The advantage, now, goes to Moderna and Pfizer-BioNTech, a biopharma analyst writes.

With mRNA vaccines further ahead in their rollouts and no safety issues cropping up so far, those programs are in a prime position to benefit, Cantor Fitzgerald analyst Louise Chen wrote to clients on Wednesday.

Even after Wednesday's meeting of the CDC's Advisory Committee on Immunization Practices, the J&J pause will continue. Experts opted against making any immediate decisions and will hold another meeting soon.

“One important thing doctors pointed to during today’s meeting is that because of the availability of alternative mRNA-based vaccines, there is less urgency for an immediate recommendation around J&J’s vaccine,” Chen wrote in her note. “We think recent developments show that safety concerns around adenovirus vaccines come at the benefit of mRNA vaccines.” 

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Pfizer and Moderna are delivering a combined 14 million vaccine doses per week to the U.S., so experts believe there's time to gather more information before the fate of the J&J shot is decided. 

Looking forward, much more should be known when the ACIP presents further findings next week, Chen wrote. Many J&J vaccine recipients have yet to clear the two-week window in which six severe blood clot events in the U.S. have occurred.

"Additional cases are expected to be captured/reported quickly, if they exist," Chen noted. "The Vaccine Adverse Event Reporting System (VAERS) is updated weekly every Friday, and we are interested in seeing updated AE reports for the vaccine."

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After news of the J&J vaccine pause, the European Union announced that Pfizer and BioNTech would accelerate delivery of 50 million doses of their vaccine, bringing total supply to the bloc up to 250 million by the end of June.

In addition, Pfizer’s CEO Albert Bourla said the company would deliver 20 million more doses to the U.S. than promised by the end of May, bringing the total supply to 220 million. Pfizer is also on track to deliver the United States' full order of 300 million doses two weeks early, he said.

Meanwhile, the European Union planned to not renew contracts beyond 2021 with J&J and AstraZeneca, another adenovirus vaccine with safety concerns, reports said.