Whatever happened to "Herd Immunity"?
Blood donations show 83% of Americans have coronavirus antibodies!
Fri, September 3, 2021, 4:47 PM
More than 80% of Americans have coronavirus antibodies acquired through infection or vaccination, according to a new study of over 1.4 million blood donations across the U.S.
The study, published Thursday in the journal JAMA, included blood samples of Americans 16 and older collected by 17 different organizations from all 50 states, Washington, D.C. and Puerto Rico. Donations represent 74% of the U.S. population, researchers said.
Estimates show that from July to December 2020 — before vaccines were available — the percentage of Americans 16 years or older with coronavirus antibodies from infection jumped from 3.5% to 11.5%. By May 2021, the percentage of Americans with infection-derived antibodies increased to about 20%.
But when researchers combined the number of people with antibodies from either infection or vaccination, they found about 83% of Americans had earned them.
Herd immunity can be reached when enough people in the population have recovered from a disease and have developed protective antibodies against future infection.
However, there are some major problems with relying on community infection to create herd immunity to the virus that causes COVID-19
It takes far more than one study with lots of limitations to conclude that 83% of Americans have been either infected or vaccinated. Did you read the study?
This was done on a select population - blood donors in metropolitan regions who differ from the general population in measurable demographic variables. "significantly more blood donors in the study were non-Hispanic White (85.0% vs 61.2%) and aged 50 to 64 years (36.5% vs 24.4%); significantly fewer donors were aged 16 to 29 years (12.1% vs 24.1%), Hispanic (6.2% vs 17.1%), non-Hispanic Asian (2.9% vs 6.2%), or non-Hispanic Black (2.5% vs 12.7%) "
Also, "donations from donors with a known vaccine history, 73.3% were from donors who self-reported receiving a previous COVID-19 vaccine, compared with CDC estimates that 57.0% of US adults aged 18 years and older had received 1 dose or more of vaccine by May 2021. Blood donors are more likely than the general US population to be employed and have attended college, factors potentially associated with increased rates of vaccination and lower rates of infection."
The authors of the study point out a number of other factors that may have impacted their findings. One of these is that estimates were not adjusted to account for potential waning of sensitivity after six months.
Herd immunity is very complex and depends on many factors, including how contagious the infection may be. At this point, I doubt that Americans will ever achieve herd immunity for this illness. We had a shot at it early on before it proliferated widely and if we were doing contact tracing for small breakouts to contain these. I remember when some people on this forum were believing that no restrictions, protections, or vaccinations were needed, and estimates were presented that as low as a 20% infection rate was sufficient for herd immunity.
What is known at this point is that the Delta variant is far more contagious and more likely to cause serious illness. We know that those who have been vaccinated are far less likely to have symptoms, need hospitalization, or die. While vaccinated people can spread it even without symptoms, it seems that they carry the viral load in their nasal passages for a shorter duration, making them less infectious to others.
Reasonable conclusions from this -- that vaccination helps a lot but that it is still necessary to use other protective measures to limit contagion. Good masks worn properly offer protection as well as avoiding crowds and indoor spaces, especially when there is insufficient ventilation.
This virus is a moving target. There has been a remarkable amount of data collected in a very short period of time. We've developed what is probably the most effective vaccines ever with amazing speed. The immune system and virology are very complex with much more yet to be understood. The more time we have, the more lives can be saved by more data about the most effective vaccines and the rate of waning immunity as well as advances in therapeutic treatments for those infected. Instead of posting "gotcha" posts that induce distrust of science or amplify quackery, we would be better served by posts pointing to logical conclusions that help protect us best at this moment which can change as the virus mutates and as we learn more.