One of the questions I’m asked most frequently is when we will have a Covid-19 vaccine. To that I say, the question is not when, but if. If we don’t have a vaccine, we don’t yet know how safe and effective it will be.

Given our well-documented difficulty developing coronavirus vaccines for SARS and MERS, and now the less than promising data from recent studies involving humans and nonhuman primates, we can’t be so sure that the current race to produce a Covid-19 vaccine will end in certain success. We don’t know whether the vaccine will offer sterilizing, long lasting immunity—as hoped—or only transient, partial protection, as seems more likely.

What we do know is that public acceptance of a Covid-19 vaccine will play an outsized role in our ability to get as many people vaccinated as possible—and to that end, it isn’t too early to begin planning our efforts to educate the public. As a new analysis published in JAMA makes clear, early planning and public education is a must. To proactively confront barriers to Covid-19 vaccine acceptance in the United States, its authors argue, we must ramp up public health education now.

The authors begin with the premise that anything short of broad acceptance of vaccination risks failure. They write, “Given that certain individuals will be ineligible for Covid-19 vaccination due to age, immunocompromise, and other preexisting medical conditions, a vaccine refusal rate greater than 10% could significantly impede attainment of this goal.”

The goal in question is that of population immunity, generally referred to by the unfortunate name of “herd immunity.” Why is such a high acceptance rate needed? A major consideration is that a Covid-19 vaccine, like most vaccines, is likely to be ineffective for older adults. As we age, the immune system loses its ability to respond to vaccines for new diseases. This is a problem, since in this case it is the elderly who are most vulnerable to Covid-19—and most in need of protection.

To help limit exposure of the elderly to Covid-19, a vaccine must limit the total number of infected people in the population from whom they may contract the virus. I believe that most people aren’t aware that the most vulnerable population is least likely to benefit directly from a Covid-19 vaccine, no matter how effective it may be. Their health and safety depend on low infection rates in the general population.

The authors identified points of resistance to vaccine acceptance. These include:

Questioning the necessity for a vaccine.

Questioning the safety of a vaccine.

Vaccination as a matter of freedom of choice.

A general suspicion of the health care system.

The authors did not mention the anti-vaccine movement explicitly, but its shadow looms large. Combined, these barriers have the power to prevent efforts to control the epidemic through any vaccine that may be developed, no matter how safe and effective it is.

Consider also the projection of these issues onto the world stage. Availability and acceptance of the vaccine globally is as important as it is locally. Recall that the infection of one person many thousands of miles from our shores has infected more than 1.7 million Americans—and the count is still rising.