Earlier this year, when the coronavirus first started to spread, almost nobody was immune. With no resistance, the virus spread quickly across communities around the world. The numbers suggest the virus is slowing down now, but at the same time, we can still see flareups and hotspots. What will it take to stop the virus dead in its tracks? The answer is it will require a significant percentage of people to be immune. How do we determine how many are needed and how do we get there are the key questions.

Suppose 100% of the world’s population was either vaccinated or had recovered from having Covid-19. At that theoretical state, the virus would have nowhere to attach itself and attack healthy cells. Presumably, the virus would crumble to the earth and or at least peter out. Since we are not at the 100% theoretical state, could we achieve herd immunity at 90%, 80%, 50%, or even less? Experts don’t agree. At this stage of the pandemic, it is amazing how much has been learned, but also how much is still not understood.

The pandemic is global, but a herd could be developed in a country, state, county, city, or even a neighborhood. Suppose 80% of a community is immune to the virus, four out of five people who encounter someone with the disease won’t get sick and could not spread the disease any further. In other words, the spread would be kept under control. Some researchers believe herd immunity can be achieved at 10 to 20 percent. The NY Times reported they were in the minority.

Chickenpox, measles, mumps, and polio are examples of infectious diseases once very common but now rare in the U.S. because vaccines helped to establish herd immunity. The threat of outbreaks of these diseases would only occur in communities with lower vaccine coverage. This is what happened in 2019 with the measles outbreak at Disneyland. If the forecasted rate of turning down vaccinations is 30% as some forecast, the herd immunity for coronavirus could be stymied.

Most experts agree we will need at least 70% of the population to be immune to have herd protection. If we do not discipline ourselves to physical distancing, hygiene, and masks the virus could get us to the high level in a few months. The downside is our hospitals would be overwhelmed and high mortality would follow. If we can maintain or hopefully reduce current levels of infection until vaccines become available, we may achieve herd immunity within a year. 

In the past, with diseases like chickenpox, some intentionally exposed themselves to the disease to get it over with and hope for early herd immunity. Not a great strategy, but it might actually work with chickenpox-like diseases. But, not with Covid-19. The reason is the current data suggest, according to some experts, Covid-19 mortality is 10 times higher than the flu. It is even higher among vulnerable groups like the elderly and people with weakened immune systems. It would be foolish to gamble with our healthcare providers.

From all I have read, I feel there are reasons to be optimistic. The research community and pharmaceutical companies are on a tear to get vaccines to market. There are many unknowns about the spread from children, the control of mass gatherings, the level of contagious spread, and other societal issues. However, I believe what we know for sure is social distancing, hygiene, and masks are the best defense we have. If we don’t throw in the towel, we will become part of the herd.