We all benefit from vaccines, whether we take them or not

DEAR DR. ROACH »

A recent column on vaccines left me unable to complete all the dots.

An 80-yearold who has been sick only once (from a vaccination) stated that he/she will never willingly accept another vaccination. You conclude your column by suggesting that by being 80, this person should look forward to a vaccine for coronavirus. If I were that writer, my immediate question to you would be, “Why?”

It would seem the writer’s immune system has proven successful for an 80-year journey. Is there greater risk beyond 80?

— J.R.

ANSWER » A healthy immune system is a large part of why a person has had good health until their 80s, but the writer, like everyone in a modern society, has benefitted from vaccines, even if he didn’t take any.

When the vast majority of a population is vaccinated against an infectious disease, even those who are not medically protected are unlikely to get the disease since it doesn’t have ongoing transmission. This is called “herd immunity.” Although herd immunity can happen through vaccination or natural infection, it may only be maintained through ongoing vaccination. Intermittent outbreaks will occur once the number of unprotected people becomes high enough.

In the case of a new infection, never seen before in the population, there is no herd immunity and the infection can spread rapidly. When, like COVID-19,

the infection is both highly infectious and can cause severe disease and death, it is exceptionally dangerous. People over 80 are particularly at risk. That’s why a vaccine is so urgently needed: to protect our most vulnerable, especially those who cannot get vaccinated (due to medical conditions), choose not to (which is unwise) or in whom the vaccine does not work (since no vaccine is perfect).

Contact Dr. Roach at ToYourGoodHealth@med. cornell.edu.