It's all riding on a vaccine. While new or repurposed therapeutics may lower the death rate from covid-19 to some degree, most experts feel the only way to avert millions of deaths in the coming months and years is the availability of an effective inoculation against SARS-CoV-2, the novel coronavirus that has killed over 1.2 million people and infected more than 50 million others.
Yesterday, Pfizer and BioNTech announced that its candidate vaccine is "90% effective" in preventing covid-19. So far, over 30,000 people have been enrolled in their randomized placebo controlled blinded trial. Of the 94 confirmed cases, most occurred among people who received a placebo injection, not the actual vaccine.
This alone is cause for celebration. Potentially. Many important questions remain unanswered. The first point that bears understanding is that "90% effective" means that many fewer test subjects who received the two-dose series of the real vaccine candidate developed symptomatic disease—the constellation of symptoms we call covid-19 disease. That does not necessarily mean that 90% fewer people became infected with the coronavirus itself. That's important because if a vaccinated person can still be infected, they might very well be able to pass along the disease to others who in turn may develop life-threatening covid-19, even if they themselves are at far lower risk of developing symptoms, let alone a bad or life-threatening case. Moreover, the fact that 90% fewer people who received the vaccine developed symptomatic disease could still end up being a kind of statistical mirage. We know that overall fewer than 1 percent of persons die as a result of being infected with SARS-CoV-2. If it turns out that those people are all among the 10% of the cases that still develop symptomatic disease despite vaccination, then today's results will have been highly disappointing in the final analysis. This isn't to say that this is what happened. Rather, Pfizer released one piece of information—"datum" not "data." We are waiting and wanting more.
For example, if this vaccine works as well as is hoped and hyped, for how long will it provide protection? (The vaccine uses mRNA vaccine technology that has only recently become feasible and has never been approved for similar purposes). Does the vaccine protect the elderly? Does it protect those with immune system dysfunction? All of these questions linger. But perhaps the single piece of information we most need that could signal that we are truly closer to being able to cast our masks aside and end our physical distancing efforts is whether or not the vaccine prevents infection and spread of the disease. If it does, 2021 will see the beginning of normalcy, though rollout will take many months or longer.
Other vaccines are in the offing as well. Some may turn out to have fewer side effects. Some may work as well or better than this one. Some may not require storage in -80°C freezers—a rarity in some parts of the country, and certainly in some regions of the world.
Today's news, though, exceeds expectations. The trial was designed to be "successful" even if it was found to be far less than 90% effective at preventing symptomatic disease. In that light, and with data from other vaccines expected in the weeks and months ahead, there is cause for more than our usual "cautious pessimism," and perhaps reason to enjoy a moment of measured optimism.