A fourth dose of a COVID vaccine may be “necessary” to protect populations against COVID-19, Pfizer CEO Albert Bourla said on March 13, wading into a debate among public health officials over whether the emergence of new COVID variants means we’ll all need a second booster shot.

“First of all, we try very diligently to stay ahead of the virus because…many variants are coming and Omicron was the first one that was able to evade [vaccines] in a skillful way,” Bourla told CBS on March 13, adding that while a third dose of a COVID-19 vaccine is “actually quite good for [preventing] hospitalizations and deaths…it’s not that good against infections.”

In January, Dr. Anthony Fauci, the chief medical adviser to the Joe Biden administration, suggested that he would need to “see what the result of the third dose is” before deciding whether a fourth dose would be needed for the wider U.S. population. U.S. federal guidelines already allow a fourth dose for immunocompromised individuals.

Data from the U.S. Centers for Disease Control and Prevention (CDC) show that while a third dose of a COVID-19 vaccine helps prevent hospitalization from the Omicron variant, protection from a third dose may start to wane after just four months.

Public health officials around the world are considering whether to roll out a fourth dose of COVID-19 vaccines later this year to bolster waning immunity from existing vaccinations and better protect against new variants. On March 11, Bourla said Pfizer was compiling data on a potential fourth dose for the U.S. Food and Drug Administration, though he noted that the regulator would “need to make their own conclusions.”

Providing a fourth dose may prove to be a logistical challenge for the U.S., which is already struggling to give people a third vaccine dose. Only 29.1% of the U.S. have received their third dose.

Pfizer’s COVID vaccine has helped to drive record revenues for the drugmaker. Pfizer recorded almost $37 billion in revenue (out of a total of $81.3 billion) last year from COVID vaccine sales alone. The company expects to sell an additional $32 billion in COVID vaccines this year, alongside $22 billion for its COVID pill Paxlovid.

Yet Bourla says Pfizer is developing vaccines to get society back to “the way we used to live” and says the drugmaker is working to develop vaccines that could protect against all variants and provide protection for at least a year.

Last week, in an interview with CNBC, Bourla said, “We can’t have vaccines every five, six months.”