Vaccine?10 Nov 2020 05:15
Nature reporting:
https://www.nature.com/articles/d41586-020-03166-8
It’s also unclear whether the vaccine can prevent people who show no or only very mild symptoms of COVID-19 from spreading the coronavirus. A transmission-blocking vaccine could accelerate the end of the pandemic. But it will be difficult to determine if the Pfizer vaccine, or others in late-stage trials, can achieve this, says Krammer, because it would involve routinely testing trial participants. “You can't do that with 45,000 people,” he says.
Another missing detail is how well the vaccine works in different groups of trial participants. “We don't know yet if it works in the population that needs it most which are elderly,” says Krammer. Because of the small number of cases it will accrue before ending, the Pfizer trial is unlikely to determine conclusively the vaccine’s efficacy in subgroups such as over-65s or African Americans, says Offit. But he adds that if the trial enrolled enough participants from such groups, it may be possible to generalize the vaccines’ likely effectiveness in these groups from its overall efficacy. In the press release, Pfizer and bioNtech reported that 42% of participants had “racially and ethnically diverse backgrounds”.
Lasting immunity?
One key unanswered question is how long the vaccines’ effectiveness will last. Based on when the trial started and previously published data on immune responses in early-stage trials, many trial participants are likely to still have high levels of protective antibodies in their blood, says Rafi Ahmed, an immunologist at Emory University in Atlanta, Georgia. “To me, the main question is what about six months later, or even three months later,” he says.
There will be a chance to answer that question if the trial continues for several more months, says Ahmed. Answers could also come from analysing the immune responses of people who took part in early-stage trials of the Pfizer vaccine, some of whom may have been given the vaccine up to 6 months ago. And although little is known about the vaccine’s long-term effectiveness, that is unlikely to hold up its use, says Ahmed. “I don't think we should say, ‘Well, I’ll only take a vaccine that protects me for five years.’ I mean, that could be crazy.”
To many known unknowns for me!!
5 Minute test anyone???
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