A Dozen Observations About COVID-19 Immunity
(Blog initially published in Tom Frieden’s LinkedIn account : https://www.linkedin.com/pulse/dozen-observations-covid-19-immunity-tom-frieden/)
Immunity is tricky. We think of it like armor – if we’re immune, we’re protected. But it’s much more complicated. Every day, we learn more about immunity to SARS-CoV-2, the virus that causes COVID-19. On balance, what we’ve learned is good news, but there are important caveats and implications.
First, the good news:
1. Recent laboratory studies suggest – but don’t prove – that immunity from infection with SARS may last many years.
2. These same studies suggest that antibodies, which have been a focus of research, may not be the only, or even the most important component of our immune response.
3. Animal studies suggest that infection protects against re-infection, at least in these animals, at least in a laboratory model, at least for a few weeks.
4. A small but interesting study suggests that neutralizing antibodies in people may be protective against re-infection, at least for some time for some people. It’s not enough to bet your life on, but it’s enough to be optimistic about the potential for immunity.
Now, the caveats:
1. We don’t know how long immunity, if it occurs, will last or how complete the protection is. Overconfidence could lead individuals and communities to let their guard down, which could result in more spread and more death. Testing positive for antibodies does NOT mean you’re immune.
2. We don’t know what proportion of people with natural infection will become immune.
3. We don’t know if some people who get vaccinated will develop harmful immune over-reaction.
4. Even if 20% of the US population has been infected, we’re nowhere near herd immunity. Not all infected are necessarily immune, and, more importantly herd immunity likely requires at least 60% infection rates, and in any case isn’t an on-off phenomenon. When more people are immune, infection spreads more slowly. But because spread is uneven, communities remain vulnerable even if a high proportion of the population has been infected. Getting to herd immunity in the US would require hundreds of millions of infections and at least a million more deaths. That’s not a plan, that’s a catastrophe.
And now, the implications:
1. The likelihood that an effective vaccine will be found is increasing. Why? Because Mother Nature usually does better than our best vaccines, and the ceiling of vaccine efficacy is usually protection after natural infection. But vaccination won’t be quick or simple. We have to ensure it’s safe, effective, available, and trusted.
2. We need to be particularly careful about vaccine safety. Developing immunity — either through infection or vaccination — may result in severe illness. This is why some people get so sick with COVID-19, and likely why dexamethasone, a medication that weakens the immune system, helps some severely ill patients. It’s a concern with vaccination, which could potentially harm a small proportion of patients because of immune over-reaction – either from the vaccination itself, or from exposure to the virus after vaccine-induced immunity. This is being studied in the vaccines being developed and will need to be tracked whenever they are given.
3. It’s possible, once vaccination is widely available, that immunity passports – certificates of immunization (or, potentially, of protective immunity from infection) will become a reality. This is already done (not well) for Yellow Fever. If it helps us reclaim our education, jobs, and economy, this could be a good thing – but there are important risks to be considered. (We outlined some controversies: “…perverse incentives, muddled risk communication messages, violations of patient privacy, diversion of resources, fraudulent certificates, and creation and perpetuation of inequalities, among others.”)
4. We can get to a new normal if we improve control today, stay apart, work together, and prepare for vaccination if and when it becomes available. For now, we need to continue to wear masks, watch our distance, and wash our hands. Our schools and universities need to be extraordinarily careful. In most of the country, we need to keep our bars closed, indoor dining closed, and avoid closed indoor spaces with lots of people present. There may be light at the end of the tunnel, but immunity is definitely not just around the corner!
There’s still more we DON’T know than what we do know about immunity to the new coronavirus. Humility remains very much in order. Learn, share knowledge, discover, move forward carefully, guided by science and a focus on protecting both lives and livelihoods.