COVID-19 Immunity

Early last year we decided to call our group Let’s end COVID! The vaccines had been developed in a remarkably short time, and like many doctors, scientists, and others, we hoped that if the vaccines worked well enough and enough people got them, the pandemic would run out of steam. Herd immunity, which happens when a high percentage of people have become immune, seemed possible. Sadly, we never reached that level of community immunity for several reasons, including vaccine reluctance and resistance fueled by widespread disinformation.
Pandemics end in one of three ways. Some, like SARS in 2002-3, fade away as effective mitigation limits transmission opportunities. Some, like polio in the 1940s and mid-1950s, are ended by effective vaccines and nearly universal vaccination. Others, such as the 1918 flu, become endemic, causing occasional or seasonal waves as circumstances change and pathogens (germs) evolve.
Successful vaccines such as those for polio and measles have created unrealistic expectations. Not even these highly effective vaccines can make everyone absolutely infection-proof, in part because many antibodies – your front-line troops in the fight – fade over time after the immediate threat is over. This is why COVID vaccines require boosters. It’s why the tetanus shots that we get after stepping on a rusty nail must be renewed every ten years. It’s normal.
Another reason why vaccines may not end pandemics is that some viruses evolve so quickly. We have seen this repeatedly during the COVID-19 pandemic. The Delta variant made people sicker than the original virus. Omicron tends to cause milder illness but spreads much more easily, so it not only makes more people sick, but it creates many more opportunities for new, potentially more dangerous variants to evolve.

By this past February almost 60% of Americans had been infected with COVID according to a Centers for Disease Control and Prevention (CDC) report released last week. The greatest increases in seroprevalence (a test for COVID antibodies in the blood) were in the age groups with the lowest vaccination rates. The COVID vaccines currently available have been very effective and fortunately still are.
But what about “natural” immunity?
At least some people, perhaps influenced by the use (and sometimes the misuse) of “natural” on food labels and other products, understand “natural” to be better than “artificial” or manufactured. Is this true for COVID immunity?
Just about everyone knows that after recovering from a viral infection we are less likely to get the same thing again. This is because our immune systems remember how they responded to the first infection. Not having to start from scratch, they can make new infection-fighting cells more quickly than before. This is how vaccines work, too. By harmlessly imitating viruses they teach the immune system to recognize and respond to the real virus when the time comes.
This does not mean that if you have had COVID once you’re safe. You can still get reinfected, just as vaccinated people can have breakthrough infections, especially if they had COVID before Omicron. But having had COVID before gives you some protection. How much protection it provides depends on several factors, including your age, the strength of your immune system, and even how sick you were. (The sicker you are, the more antibodies you make.)
It also depends on what variant you get. Another recent study found that previous infection gives about 90% protection from getting COVID from the Alpha, Beta, and Delta variants, but just 56% against the dominant and much more transmissible Omicron.
How long immunity lasts matters too, and that relates to some of the same factors, including age and immune system health. Some studies, including one published last month in the New England Journal of Medicine, have found that natural immunity can last as long or longer than vaccine immunity. But getting COVID to gain immunity is dangerous. The risk of severe disease, hospitalization, even death, is high. It’s impossible to know in advance how sick you will get.
Besides, after even an infection with mild symptoms or none at all, the possibility of developing life-changing long-COVID is too big a risk.
If you have never had COVID, vaccination is the safest, most dependable way to protect yourself and people around you. If you have had COVID, there is an even better reason to get vaccinated. Numerous studies show that getting vaccinated after having COVID creates a hybrid immunity that is stronger than that from infection or vaccination alone and protects better across variants.
Respect the mask. Protect the vulnerable. Get the shot. Get boosted. Maybe we can still end COVID.

Michael Heyd, a retired medical librarian from Fairfield Township who spent more than forty years searching the literature for professional hospital staff, is a member of Let’s end COVID!.
Published: 5/7/22

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