Why are precautions necessary if we’ve had vaccine?

Dear Dr. Roach: Can you elaborate on how the COVID vaccine is different — or inferior, or maybe just not as fully tested — from other vaccines? As far as I know, we do not need to continue to take precautions for polio, or the Spanish flu or bird flu — those vaccines protect us. Why the need for continued precautions for COVID after being vaccinated? — W.S.

Dear W.S.: The COVID vaccines are new, but the evidence is mounting that in the real world (as opposed to just studies), these vaccines are very safe and effective. Part of the continued caution in the current COVID-19 pandemic is due to the unknown duration of the effect of the vaccine, but much of the concern has to do with just how many people are infected.

There is the possibility of a new variant becoming prevalent that might be more contagious, more deadly, less amenable to our therapies or able to overcome the resistance conferred by the vaccines. In fact, there are variants that are more contagious and perhaps more deadly, but, so far, the treatments and vaccines continue to cover the new variants pretty well.

We certainly hope the vaccines will continue to provide a high level of protection. It’s the emergence of these variants that currently concern our public health officials the most.

I should note that without continued vigilance, there remains the possibility that polio could return, and every year brings the concern of a new influenza strain, such as swine flu or bird flu. This year, social distancing and mask use dropped influenza transmission to historic lows.