COVID-19 vaccines may become a viable business. That’s a problem.

For most of us, the growing evidence that the efficacy of COVID-19 vaccines is declining over time should be a cause of worry. For the drug companies that have spent billions of dollars developing them, it’s a once-in-a-lifetime opportunity.

Recent studies on vaccine effectiveness have led to a run of orders for boosters in recent weeks. The U.S. will start distributing extra shots beginning Sept. 20th and expects to roll out about 100 million doses in the coming months.

Shortening the window before a third dose from eight to as little as five months was being discussed, President Joe Biden said last week. The U.K. last week ordered 35 million more doses of the Pfizer Inc. vaccine to supplement earlier shots. In Israel, anyone over 30 is already eligible for a booster.