Well, that means what is the current thinking as of 11:21am 4/19/2020… Things change fast in this pandemic and those of us trying to provide you with the most accurate and reliable information are working hard to stay abreast of the newest info.
First let’s review the concept of vaccines. The purpose of a vaccine is to 1) introduce immunity to either the person vaccinated or to the person and their community that 2) is effective against infection and lasts and 3) does not unacceptable risk, usually side effects or vaccine complications. Let’s look at a simplified example of vaccine development before discussing a potential COVID-19 vaccine. Polio vaccines are a great way to begin the discussion.
The live polio vaccine (Sabin vaccine, introduced in 1955) is an oral weakened/live virus vaccine against polio while the inactivated polio vaccine (Salk vaccine, introduced in 1961) is an injected form made of viral proteins. The Sabin vaccine is much more effective at preventing polio disease in an individual and also is the only polio vaccine that provides immunity for others in the community. When we had polio in our US communities in the 1950s, at its peak each year there were 60,000 American children infected, 3,000 children who died, and only 1 out of 10 who recovered fully. In that situation, it was important to induce herd immunity and to give the most effective vaccine, i.e. the oral Sabin form. This was done with the knowledge that 1 in 1,000,000 America children would contract polio and potentially die from the vaccine. This may sound unacceptable, but know that there are no risk free vaccines or activities in this life on Earth. We must weigh the risks with the benefits. We knew of the Sabin vaccine risk at the time and yet our US communities flocked to get the new oral polio vaccine because they understood the risk of disease was profoundly greater than the vaccine. Obviously, for each individual person who is exposed to polio, whether from the live vaccine or the virus, the disease is acquired or not, which feels like 100% or 0%. But when we talk about the overall risk, at that time it was riskier to chance the live infection vs the live vaccine.
Once our numbers of polio cases dropped below 1 per 1,000,000, the risk of the oral vaccine outweighed the risk of the disease, so from a public health standpoint, it was time to switch to the injectable Salk vaccine. The price we paid? The Salk vaccine is not as effective as the Sabin oral vaccine and does not provide herd immunity, but at that phase of polio infection in the US, we did not need herd immunity. Since 2000, we have only used the inactivated Salk vaccine in the US and with giving multiple, precisely timed doses we have greatly improved the efficacy. As long as we keep enough herd immunity to polio and as long as our number of cases of polio are low, this is the best vaccine to use to maximize benefit and reduce risk.
So here we are with a new virus in our American communities, that like polio is remarkably contagious, yet has a very different range of disease that it produces in humans . I am proud of all of our communities for how we have reduced the pandemic and prevented unnecessary death with our so-called “NPI”s or non-pharmaceutical interventions (quarantine, social distancing, stay at home orders). Yet this week we will have 60,000 American deaths from the disease in the US. The next phase of managing this epidemic becomes interesting: we don’t have a specific anti-viral medication for COVID and we have no vaccine, yet we need to move past our NPIs while minimizing risk to the more susceptible individuals in our communities. We need to prevent unnecessary death and suffering. Now let’s move on to the theory of a COVID vaccine.
COVID-19 is a coronavirus, a large group of varied RNA viruses that infect mammals and birds. Veterinarians would love to have a coronavirus vaccine for animals since coronaviruses cause death and illness in domestic cats and chickens. Yet animal coronavirus vaccines have been unsuccessful: despite many attempts, animal coronavirus vaccines either have too many side effects, do not induce lasting immunity against infection, or don’t induce any immunity at all. In fact several animal coronavirus vaccine attempts showed significant reactions to the vaccine that caused unacceptable animal death and disease.
In humans, we have coronaviruses every single winter, but they usually cause a plain “cough and cold” in children, a minor infection at most. We humans have had several other serious coronavirus infections recently, including SARS and MERS in 2002 and 2005. Because those illnesses were so much more serious, they were vaccine candidates. Only SARS came close to having an effective vaccine, but that coronavirus was (thank goodness) not very contagious and the infection died out with NPIs and the natural low contagiousness of the virus. Also, the SARS vaccine- in testing- showed a concerning/scary side effect: it caused significant lung damage and disease in animal models. Other virus vaccines to Dengue and RSV have had similar terrible side effects.
Now we move into vaccine development for COVID-19. So far we have an impressive multinational effort that has moved very quickly in both government and private entities. We all need to respect and defer to the vaccine experts for this phase of the COVID-19 fight, yet you should be aware that a COVID-19 vaccine is not a guarantee. Remember that an effective vaccine needs to 1) produce immunity in the individual +/- the community that 2) lasts and is effective and 3) does not induce too much group risk, such as disease or harmful immune reactions.
Will we have a COVID-19 vaccine that is similar to the flu shot? We might. The constant change and mutation of coronaviruses might require that we produce “a” vaccine to COVID-19 that changes yearly like our influenza vaccine. The flu shot provides, on average, 40-70% protection against infection and even better protection against severe disease and hospitalization. It is absolutely key for individuals at risk for severe disease. And by taking the flu shot, we produce- over years- a herd immunity against strains of flu.
We’ll see what the COVID-19 researchers are able to develop. In the meantime, it’s all about NPIs. Wash your hands. Don’t touch your face. Minimize your risk to others by following your community’s rules for social distancing. Take special care of the babies and your older folks.
Here’s Dr. Anthony Fauci’s recent video on this topic.
