February 22 was a day in which the country set a milestone; the U.S. saw its 500,000th Covid-related death since the onset of the pandemic. No sooner had the two Covid-19 vaccines received their emergency use authorizations (EUAs) and medical authorities began talking of one day reaching something called “herd immunity.” This is an infectious disease term that born of preventive medicine’s successful development and implementation of vaccines. There are two mechanisms through which the body can become immune to a pathogen. The “natural” way is to contract the disease and successfully fight it off. The other mechanism is by “inducing” immunity through introducing a harmless piece of the pathogen (bacteria or virus) into the the body. By doing so the immune system can recognize the pathogen and learn to make antibodies against anything that “looks like” what was introduced in the vaccine. In the Covid-19 vaccines each vaccine used a portion of the “spike” proteins that coat the outer layer of the virus. The new variants have modified spike proteins to make its entry into cells easier. To ensure that our immune system will be able to recognize the modified virus, booster shots are being developed that will adjust for these modifications. The longer the pandemic continues, the greater likelihood that more variants will appear. Herd immunity will be achieved when enough of the population have achieved “natural” immunity from infection and enough of the remaining population have been vaccinated so that the infection is no longer a threat to the community. We have already achieved this with most childhood illnesses thanks to aggressive vaccination campaigns among Pediatricians and Family Practitioners.
Originally most authorities were predicting that approximately 75% of the population would need to be vaccinated with the Covid-19 vaccines to achieve herd immunity. At this point we have not even approached the 10% vaccination level yet we are seeing dramatic declines in infection numbers throughout the country. This decline has led to the belief that we could achieve herd immunity much sooner. Authorities feel the decline in numbers suggests a high level of natural immunity has already been achieved. We have numbers of those who were tested and found “positive” but authorities suggest countless others who were never tested had a Covid-19 infection with few or no symptoms. Perhaps this large body of “natural immunity” accounts for the drop in infection rates. Although researchers are unsure how long antibodies persist from a natural infection, if T-cell activation takes place the protection could be long-lived. It is still being recommended that those who have recovered from a active infection should eventually receive a single dose of either of the mRNA vaccines. But if the predictions of many of these medical experts are to be believed, herd immunity may occur as early as this Spring or Summer. Take heart because we are almost there!