Pfizer's coronavirus vaccine requires 2 shots given 3 weeks apart, which could make distribution more complicated
coronavirusvaccine candidate is more than 90% effective in preventing COVID-19, the company announced Monday.
- The vaccine involves two shots administered three weeks apart.
- People may later need additional booster shots too, experts say.
Pfizer's coronavirus vaccine candidate is now leading the pack, with emergency authorization expected from the Food and Drug Administration within weeks.On Monday, the pharma giant and its German partner BioNTech announced that their vaccine was more than 90% effective, based on 94 cases of the disease observed in an interim study.
But a two-dose vaccine comes with supply-chain challenges and the possibility that not everyone will return to a doctor's office for the critical second dose.
Double troubleA double-dose vaccine requires twice as many vials, syringes, refrigerators, and clinic visits at a time when such resources are already limited.
For example, research shows that less than one-third of young women who got the first shot of human papillomavirus vaccine (HPV) — which primarily targets viruses than cause cervical cancer — return for the remaining two doses to complete the series.
We'll likely need booster shots
Such challenges could further snowball if it turns out that people need to get revaccinated regularly.Scientists haven't been able to study the new coronavirus long enough to determine how long immunity lasts, but some evidence suggests people could get reinfected. Research has found that that coronavirus antibodies dissipate after a period of weeks or months, which could mean our immunity — whether generated in response to an infection or a vaccine — may be similarly transient. Our immune systems have more than just that line of defense, though, so many questions remain about immunity to the virus.
"If immunity does turn out to be fleeting, we'll need a plan of a vaccination plus a booster, or revaccination at periodic intervals," disease ecologist Marm Kilpatrick previously told Business Insider.
Still, it's not a deal breaker if people become susceptible to reinfection sometime after the initial shot."This happens for a lot of vaccines," Florian Krammer, a vaccinologist at the Icahn School of Medicine at Mount Sinai, previously told Busines Insider. "It's not a problem. You can get revaccinated."
Experts won't be able to determine whether boosters will become part of the protocol until vaccines get rolled out. Pfizer has said that the bulk of its doses — up to 1.3 billion — will be ready in 2021."Once we start seeing vaccine failures increasing, then we can consider booster doses. But we don't know at this stage whether that will be necessary," Orenstein said.
If it turns out that people need to be revaccinated regularly, that decreases the likelihood that everyone will get the shots they need to stay protected.Andrew Dunn contributed reporting to this story.
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