Friday, May 15, 2020

What Do We Know about Progress Toward a COVID-19 Vaccine?

There seem to me a few salient facts about the search for a COVID-19 vaccine.

1) According to a May 11 count by the World Health organization, there are now 8 vaccine candidates now in clinical trials, and an additional 102 vaccines in pre-clinical evaluation. Seems like an encouragingly high number.

2) Influenza viruses are different from coronaviruses. We do have vaccines for many influenza viruses--that's the "flu shot" many of us get each fall. But there has never been a vaccine developed for a coronavirus. The two previous outbreaks of a coronavirus--SARS (severe acute respiratory syndrome) in 2002-3 and MERS (Middle East respiratory syndrome) in 2012--both saw substantial efforts to develop such a vaccine, but neither one succeeded. Eriko Padron-Regalado discusses "Vaccines for SARS-CoV-2: Lessons from Other Coronavirus Strains" in the April 23 issue of Infectious Diseases and Therapy. 

3) It's not 100% clear to me why the previous efforts to develop a coronavirus vaccine for SARS or MERS failed. Some of the discussion seems to suggest that there wasn't a strong commercial reason to develop such a vaccine. The SARS outbreak back in 2002-3 died out. While some cases of MERS still happen, they are relatively few and seem limited to Saudi Arabia and nearby areas in the Middle East. Thus, one possible answer for the lack of a previous coronavirus vaccine is a lack of effort--an answer which would not reflect well on those who provide funding and set priorities for biomedical research.

4) The other possible answer is that it may be hard to develop that first coronavirus vaccine, which is why dozens of previous efforts to do so with SARS and MERS failed. Padron-Regalado put it this way (boldface is mine): "In vaccine development, it is ideal that a vaccine provides long-term protection. Whether long-term protection can be achieved by means of vaccination or exposure to coronaviruses is under debate, and more information is needed in this regard." A recent news story talked to researchers who tried to find a SARS vaccine, and summarizes their sentiments with comments like: "But there’s no guarantee, experts say, that a fully effective COVID-19 vaccine is possible. .... “Some viruses are very easy to make a vaccine for, and some are very complicated,” says Adolfo GarcĂ­a-Sastre, director of the Global Health and Emerging Pathogens Institute at the Icahn School of Medicine at Mount Sinai. “It depends on the specific characteristics of how the virus infects.”Unfortunately, it seems that COVID-19 is on the difficult end of the scale. ... At this point, it’s not a given that even an imperfect vaccine is a slam dunk."

5) At best, vaccines take time to develop, especially if you are thinking about giving them to a very wide population group with different ages, genetics, and pre-existing conditions.

So by all means, research on a vaccine for the novel coronavirus should proceed full speed ahead. In addition, even if we reach a point where the disease itself seems to be fading, that research should keep proceeding with the same urgency. That research may offer protection against a future wave of the virus in the next year or two. Or it may offer scientific insights that will help with a vaccine targeted at a future outbreak of a different coronavirus. 

But we can't reasonably make current public policy about stay-at-home, business shutdowns, social distancing, or other public policy steps based on a hope or expectation that a coronavirus vaccine will be ready anytime soon.