More and more people 65 and older are fortunate to be receiving their first doses of Covid-19 vaccine with more doses hopefully released soon for the rest of the population. If you are one of the lucky pioneers with the first approved vaccines, congratulations on getting a dose, or doses, as this is the first step down a long road toward rolling back the pandemic.

You should be maximally protected a few weeks after getting vaccinated, then for the next few months at the very least. Having received your vaccine, can you now go back to “normal”? As much as I would like to say yes, go out and enjoy life the way you used to, I think the data are still uncertain about the degree of protection — your risk of becoming infected if you breathe in novel coronavirus particles (SARS-Cov2) — and the length of protection — how long your ability to fight off SARS-Cov2 will last.

The two-dosage Pfizer-BioNTech and Moderna shots are messenger RNA (mRNA) vaccines. They deliver instructions (messenger RNA) into your cells, ordering them to make a spike protein from the SARS-Cov2 virus. By getting you to produce a harmless part of the virus, not the whole virus, the vaccine primes your immune system to produce antibodies specific to that component of the virus particle, so that when the real virus shows up, your immune system recognizes and neutralizes it. Johnson & Johnson’s single-dose vaccine is an adenovirus-based vaccine that delivers non-replicable antigens from coronavirus into cells via the virus. First, let me address the degree of immediate protection.

Recall that the Food and Drug Administration (FDA) provided emergency use authorization for these vaccines, and as a result we do not have the typical lengthy clinical trials to assess the duration of protection after dosing someone (once or twice). These trials are continuing, so we may eventually have more information.

Current efficacy estimates extend out to a few months following the second dose/shot. Although the immediate efficacy figures sound terrific, such as 93 percent protection for Moderna https://www.nejm.org/ doi/full/10.1056/NEJMoa2035389 and 95 percent protection for Pfizer-BioNTech https://www.nejm.org/doi/full/10.1056/ NEJMoa2034577, they vary across subgroups. For instance, I received a dose of Moderna, and if you look up efficacy for just those who were age 65+, it is estimated to be 86 percent, less than the 93 percent cited for the clinical trial sample as a whole. To put it another way, if 100 vaccinated seniors were exposed to a sufficient dose of the virus, 14 might be expected to contract the disease.

The silver lining, based on the data about severe cases, is that vaccinated seniors would most likely develop a much less severe case, avoiding hospitalization or death. The same appears to be true for the Johnson & Johnson vaccine, with 67 percent efficacy for contracting the disease and 85 percent protective against severe disease. Now, interpreting the data from the trial is complicated by the extent to which participants were exposed and, most importantly, the intensity of the viral dose they encountered. For instance, walking through a Covid-19 ward in a hospital is likely to expose you to a greater concentration of virus than walking in a park with only a few people around. We can assume that because this was a large randomized controlled trial that lifestyle differences in exposure following inoculation were not different between the placebo and the vaccine groups. However, a careful examination of the published data indicates that seniors in the placebo group were much more careful than their younger placebo group counterparts, contracting the disease at much lower rates.

The second issue these trials could not address was length of effectiveness for the vaccine because of the short duration of each trial before emergency approval was granted. We will have more definitive data about the duration of protection over the coming months. If we quickly achieve herd immunity, the holy grail for ending the pandemic, we may have difficulty knowing how effective the vaccines are and for how long. It stands to reason that when the positivity rate in the community is very low, a wonderful problem we would all love to have happen, no one in either the placebo or the vaccine condition will contract the disease.

Many vaccines seem to confer near lifetime protection, for instance, measles vaccine. That is, lifetime immunity means that once your immune system is trained to recognize the virus it always will manufacture sufficient antibodies to stop a new infection in its tracks. A caveat is that the immune response suffers from diminished efficiency in old age, a reason why seniors are sometimes given stronger doses of vaccine than other age groups. Other vaccines, like our annual influenza shots, may work for the current season only, partly because the rate of mutation is so high in flu viruses.

Another unknown is whether you could still become contagious after inoculation when being exposed to the virus. That is, would you manufacture sufficient Covid-19 virus particles to infect someone else before your own immune system could snuff out the infection?

The other risk for those vaccinated with these early vaccines is that one or more mutant variants will begin to replace the original SARS-Cov 2 virus and potentially escape from the clutches of the current vaccines as some fear may be happening with the so-called South African variant. This form of “hide and seek” between viruses and our immune systems has been going on for millennia, and we are fortunate that our immune system has multiple weapons to fight viruses, bacteria, fungi, and other invaders.

So, what should we do a few weeks after getting our vaccinations? Be cautious and do not drop the current good habits you have already adopted, such as masking, social distancing, avoiding crowds, and frequent hand washing. (Here’s what the CDC recommends, as of March 8, for those who have received the vaccine: https://www.cdc.gov/coronavirus/2019-ncov/vaccines/fully-vaccinated-guidance.html.) But, you may consider resuming activities that you dropped, such as shopping in non-crowded stores, eating in restaurants either outside with patio seating or inside with adequately spaced tables.

Each of us has different risk thresholds, and you probably know your tolerance for risk. I’m a cautious type myself. Resumption of normal activities and a mask-less approach to living seems to be some time away, likely by 2022, following achievement of herd immunity associated with widespread vaccination rates and the resulting decline to low infection rates in the community. In the interim, encourage your friends, family, and neighbors to get their vaccinations, assuming that they are good candidates based on CDC guidelines.

The sooner we can reach herd immunity, the sooner we can return to a pre-Covid 19 lifestyle.