As regular readers of these posts know, I consider vaccines to be one of, if not THE, major achievements of medical science. Vaccination has literally saved millions of lives over the years. Diseases such as polio, whooping cough and measles that killed children around the world should now be of historic interest only. [Insert drum roll and consign the “anti-vaxxers” to the deepest levels of Hell.] Can they save us from Covid-19?
The traditional approach to vaccination has been a slow process. There are two major ways vaccines have been produced. Measles, mumps and rubella vaccines use a weakened form of the virus – close enough to the real thing that the body builds up defenses against it but so modified as to not cause a serious infection. Flu and polio vaccines and others use killed virus particles that cannot cause infection but which still enable the body’s immune system to later recognize the virus if it tries to infect you and fight it off. New vaccines typically take up to 10 years from conception through wide distribution, with lengthy trials proving that they are both effective and safe. The current pandemic, which has killed millions and damaged economies around the world, did not give us the luxury of many years of development and testing.
National labs and pharmaceutical companies, large and small, have rushed to develop vaccines. As of August 20, a report found 30 vaccines in clinical trials and over 100 at earlier stages of development. As you are probably aware, the two that are furthest along are vaccines from Pfizer (working with a small German biotech firm, BioNTech SE). and Moderna, which has worked closely with the U.S. National Institutes of Health. Both these groups are using a relatively new technology. They are injecting messenger RNA (mRNA) into the body. The mRNA tells the body’s cells to produce a protein, in this case the “spike protein” that is a distinctive part of the coronavirus, which then causes the body to build up an immune response. Note that in one sense this is not that different than the use of weakened live virus: the body’s own cells are tricked into producing a “foreign” substance that induces development of immunity. A different approach has been used by AstraZeneca working with Oxford University. They use a genetically altered adenovirus that carries a Covid-19 protein to develop the immune response. (This technology is also being used by Johnson and Johnson in its attempt and is the basis of the vaccine being distributed in Russia before any testing.)
How well do the Covid-19 vaccines work? A MAJOR WARNING: everything that I and most people know about these vaccines comes not from published peer-reviewed scientific papers but from press releases. The British National Health Service, which hopefully had access to full data, approved the Pfizer vaccine last week for emergency use, and the U.S. FDA is to review their application this week. Moderna is set to apply for emergency use authorization later this month. Based on the data that has been made available, both vaccines are remarkably effective, in the range of 95%. The Moderna/NIH trial enrolled over 30,000 U.S. participants, including 7000 over 65, 5000 under 65 but with high risk chronic diseases, and included 37% black and Hispanic: all high-risk groups. The AstraZeneca trial has been viewed skeptically because of a strange result. Several thousand participants were accidentally given a half dose for their first shot and full dose for their second. After this was noted, all subsequent participants got the intended series of two full doses. The study found that the vaccine seemed 90% effective in the group getting the half dose first shot but only 60% in the rest. This seems biologically implausible and is currently under study.
How safe are the vaccines? This is the $64 question for a substance that may be given to billions of people around the world. The good news is that the preliminary trials have not identified any serious side-effects, though 10-15% did experience soreness at the injection site, fever, chills and muscle aches that last 1-2 days. Whether more important side effects turn up months or years later is at this point not known.
How long will the immunity last? Again, a question impossible to answer. A recent report in the New England Journal of Medicine was encouraging: people enrolled in the very early (Phase 1) trial of the Moderna vaccine still had good levels of immunity in their blood several months after the second dose. A “real life” experiment adds to the optimism. A fishing trawler with a crew of 122 tested all the crew before they went to sea, both by nasal swab and antibodies. Even though all tested negative for the virus, one got sick with Covid and almost the entire crew subsequently fell ill. The only three who did not develop Covid were the three whose earlier antibody tests showed antibodies to the coronavirus.
When will a vaccine be available? Assuming the FDA grants approval, Pfizer and Moderna expect to deliver some 40 million doses by the end of the year. Since all current vaccines require two doses to confer immunity, this means some 20 million people can be vaccinated by late January/early February. The Advisory Committee on Immunization Practices, whose advice is usually followed, said that first priority should go to front-line health care workers, nurses and doctors working with acutely ill patients, some 21 million, and the 3 million residents of long-term care facilities, who have suffered the worst of the effects of the pandemic. Next in line would be those over 75 and such essential workers as teachers, police, fire and EMTs. By May, supplies should be much larger, particularly if vaccines from AstaZeneca and Johnson and Johnson are approved, and the entire population could be vaccinated by the summer.
Will people accept the vaccine? Vaccine skeptics abound, and the politicization of the vaccine development program certainly feeds into these feelings. A recent poll found that more than a third of Massachusetts residents were unlikely to get vaccinated, even though 90% supported requirements to wear masks, 64% were somewhat or very worried about catching Covid-19 and 66% knew someone who had been diagnosed with it. The acceptance rate is critically important, as so-called “herd immunity” will only keep the pandemic at bay if 80-90% of us are immune. Hopefully by the time there is sufficient supply for the general public, enough time will have elapsed from the early use that safety concerns will be addressed. It will also be very important for the doctors, nurses and others giving the vaccine to warn people about the potential for short-term annoying side-effects and reassure them that this shows that the vaccine is working, and ensure they come back for their second shot.
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