With any luck, one of the handful of promising Covid-19 vaccines currently going through human trials will meet with regulatory approval, maybe even in time for winter. One thing worrying public health officials, though, is what happens if a significant number of people don’t want to be vaccinated. Vaccines are responsible for saving millions of lives every year, and yet there has always been a small but hardcore contingent of anti-vaxxers that rejects the science or buys into conspiracy theories about immunizations. Unfortunately, their ranks are growing during the current crisis. National health authorities, along with the World Health Organization, are engaged in a furious game of whack-a-mole as they try to knock down the conspiracy theories and correct misinformation. Countering the anti-vaxxers is important work, but it’s only part of the picture. The bigger danger is a broader vaccine hesitancy: What if rational people who get their flu shots and vaccinate their children, and who are eager to be part of the solution to this pandemic, have worries that public health authorities and governments don’t address? The World Health Organization lists vaccine hesitancy as one of its top 10 global health threats. One in six UK respondents to a June YouGov survey said they definitely or probably would not get vaccinated. A CNN poll in May showed a third of Americans would not try to get a vaccine if it existed. Like everything else in the US, opinion on a vaccine varies along party lines, with 81% of Democrats and only 51% of Republicans keen to get vaccinated. Some of the skepticism reflects a mistrust of Big Pharma, some of it a mistrust of government. Some of it is simply because it’s been a long time since we lived in fear of the many diseases that vaccines now protect against. Dr. Anthony Fauci, the US’s top infectious disease expert, has said that a vaccine that is 70% to 75% effective but taken by only two-thirds of the public would not create the herd immunity necessary for economies to get back up and running. So governments have a lot riding on not only securing an immunization program but on making sure people take part. However, if a vaccine overpromises, if the risks are not clearly explained or if there are problems with delivery, it could further undermine trust in authorities, institutions and even experts, with far-reaching consequences for public health and the economy. It’s hard to imagine another time when there was so much riding not just on the science, but on how it’s communicated. One hurdle for health-care authorities is convincing people that a vaccine produced at lightning speed is no less safe than one that would normally take more than a decade to develop. They will have to be clear about where the uncertainty lies. For example, it’s impossible to know from even large clinical trials how vaccines will affect people with a range of different conditions; if vaccines will have adverse long-term effects; or what the impact of repeat doses might be if, as many expect, booster shots are required. Most advanced countries have developed systems for reporting adverse consequences of vaccines and medications precisely because there is uncertainty in their effects across different populations and over time. The US has the Vaccine Adverse Event Reporting System or VAERS; the UK has the yellow card scheme. While established vaccines have been linked to some rare cases of serious illness, researchers have not found a link between established vaccines and adverse impacts in most cases. This hasn’t stopped incorrect information from spreading. Confused and irresponsible messaging hasn’t been helpful either. “The fact that it’s being crunched into such a short period has been a cause for concern,” says Oksana Pyzik, a senior teaching fellow at the University College London School of Pharmacy. “We can’t really afford to cut corners in this process, specifically because there is so much momentum behind an anti-science movement.” There are other concerns, apart from efficacy and safety, that governments will have to monitor, notes Pyzik. One is the risk of fakes. The WHO says one in 10 medical products circulating in low- and middle-income countries is falsified or does not meet standards. Falsified medicines lead to poisoning, untreated disease and other hazards. And Covid-related fraud, from masks to medicine, is booming, the United Nations has found. Vaccines will be a target, too. Officials have already discovered a fake Israeli coronavirus vaccine being sold in South America. Any doubts over the quality of a vaccine, which can also be affected by inadequate storage or transport, will impact trust. And that trust was being sorely tested even before the pandemic. In the US, a near epidemic of overprescribing, especially of opioids, has increased skepticism of both doctors and drug companies. Black and minority communities hit hardest by Covid-19 might have the most reason to line up for vaccines, but vaccination rates are lower among minority groups because of lower levels of trust from historical abuses. None of this is to suggest that vaccinating isnt the right choice for society and individuals. Researchers and pharmaceutical companies are moving at a breakneck pace in this outbreak for very understandable reasons. The recent surge of cases in Europe and elsewhere underscores the imperative of finding a way past this pandemic. “It’s understandable that people are more concerned about new vaccines, but all prospective Covid-19 vaccines are undergoing extensive testing to ensure they are effective and safe,” writes Dr. Mary Ramsay, the head of immunization at Public Health England, via email. If people are to have confidence in regulators’ declarations that a vaccine is “safe and effective,” much will depend on governments acknowledging their concerns and being transparent about both the benefits and the unknowns. Pretending science doesn’t contain uncertainty serves neither the scientists nor public health. Bloomberg