Max Nisen

By Allowing Vaccine Mixing, the FDA Simplifies the Booster Rollout

The US rollout of Covid-19 booster shots has been defined, unfortunately, by confusion. Last month, the Food and Drug Administration approved additional shots for many people who had received the Pfizer vaccine, but not for anyone who’d gotten Moderna or Johnson & Johnson. And in contrast to health authorities in several other countries, the FDA did not sanction allowing people to get booster shots that didn’t match their original vaccinations.

So news that the agency may soon endorse such mixing comes as a welcome surprise. As soon as this week, it is expected to approve boosters of the Moderna and J&J vaccines as well as mixing of shots. This is the right decision, and it steers the agency toward the greater flexibility it needs.

For months, several European countries and Canada have allowed millions of people who have had a dose of a shot made by AstraZeneca PLC (not yet approved in the US) to get a second shot of an mRNA vaccine — the kind made by Pfizer and Moderna. No major safety issues have emerged.

US regulators have been understandably reluctant to approve mixing on the basis of such indirect evidence. But their caution, in this case, has led to harmful delays. The FDA has effectively prioritized healthy people who’ve had the Pfizer vaccine over people with multiple risk factors who’ve had other vaccines. In the process, it has complicated the booster process. Doctors, pharmacists and other health-care providers may have to turn away booster seekers who happen to have had vaccines other than Pfizer.

Fortunately, last week, a US clinical trial produced the homegrown data the FDA needed to approve booster mixing. Unsurprisingly, the study found that mixing shots is safe — and also that people who have received the J&J shot get more protection from an mRNA booster than they would from a J&J one. These are early results from a small study group, but they should be enough to allow the FDA to shift policy.

Once the approvals are in place, it should become far simpler for the FDA — and for health-care providers — to operate and explain the booster program. There will be no more need to arbitrarily exclude people in need. Everyone over 65 or at high risk because of health conditions or their jobs will get mRNA boosters, along with everyone who got an initial J&J shot. And there should be no logistical headaches from trying to match everyone to their initial vaccine brands.

Of course, it remains essential that the FDA maintain its high standards for evaluating the safety and effectiveness of vaccines (and all drugs). But a pandemic requires some extra flexibility and urgency. It’s always going to be difficult to strike the ideal balance, but at this moment, allowing vaccine swapping is a critical step.