VACCINE OPTIMISM is understandable in these days of anxiety about the virus. Almost every day, there are upbeat reports about a vaccine starting a new phase of clinical trials, and the worldwide research effort spans technologies old and new. Surely a safe and effective vaccine must arrive before too long — as promised, in “warp speed,” such as later this year or early next?

A dose of realism would be prudent. Vaccines are truly remarkable medicine and have proved effective in stopping diseases such as measles and polio. But they are not simple to discover, manufacture or distribute. Many research efforts fail. The first clinical trial for an HIV vaccine was in 1987, and there still isn’t one, despite much hard work. As Carolyn Y. Johnson reported in The Post on Monday, once a vaccine is found to be safe and effective, the process will be at the beginning, not the end. Vaccines must be manufactured to exacting standards. Distributing the vaccine fairly to people in the United States and around the world will strain health networks, the supply chain, public trust and global cooperation. This may take months or, quite likely, years.

Another reason for caution is that the vaccine timeline depends on human physiology. It may take a while to build up the antibodies to fight the novel coronavirus. A second inoculation may be required. Immunity could be short-lived or partial. Also, it is possible that the first vaccines to win approval may not be perfect, and not work all the time on everyone. As Ms. Johnson points out, the measles vaccine is one of the best, 98 percent effective at preventing disease, but the influenza vaccine is 40 to 60 percent effective most years, because it must be recalibrated to take into account shifting strains. Ideally, a vaccine would prevent the disease, but it is possible one will emerge that lessens severity of symptoms. For all these reasons, it is vital that the integrity of vaccine development, testing and production not be thrown into doubt by haste or political interference that could erode public trust.

It is hard to imagine, but next year — or four years from now — we could still be waiting for a vaccine.

President Trump abdicated leadership and shunted pandemic response to the states. Now, as his White House task force coordinator, Dr. Deborah Birx, stated on CNN over the weekend, the virus is “extraordinarily widespread.” We need to start anew with a national effort to mitigate and contain the pandemic in the United States. The hour is late, but not too late. We need significant quantities of personal protective equipment and high-speed diagnostic testing equipment and supplies — and if the market can’t supply them, the government must step in. Once rampant community spread is brought under control, then plentiful testing, tracing and other measures will be necessary, as well as face masks and social distancing for a long while to come.

Let’s suppose it is summer of 2022, and there is still no vaccine. What would we wish we had done today? Let’s do it.

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