The recommendation by the Centers for Disease Control and Prevention and the Food and Drug Administration to pause use of the Johnson & Johnson coronavirus vaccine — citing six women who developed serious blood clots in their brains after vaccination — could hardly have come at a worse time.


This news arrived just as vaccination eligibility was opening up and a whole new tranche of people were making the decision to either get or refuse the stick of a needle. Nearly half the eligible population has received at least one injection. Uptake is still limited by vaccine supply in many places. But as public health authorities try to reach the country’s second half — or at least enough to reach herd immunity — they will eventually be recruiting along a descending path of public enthusiasm. And any news that heightens the impression of risk makes their task harder.


Free riders are people who benefit from the public good but don’t have to pay or sacrifice for it. In the case of a pandemic, free riders are those who enjoy the positive result when other people get vaccinated — lower transmission of the virus and eventual herd protection — but refuse to take a tiny risk and get vaccinated themselves. The challenge comes, of course, when lots of people realize they can be free riders, and the public good is destroyed.