With an expanded usage recommendation from the CDC's Advisory Committee on Immunization Practices (ACIP), pneumococcal conjugate vaccines from Pfizer and Merck are poised to add millions more eligible U.S. adults into their fold.

In a 14-1 vote, the panel moved to expand its usage recommendation for both Pfizer’s Prevnar 20 and Merck’s Capvaxive to include all adults aged 50 and older as well as adults between 19 and 49 years of age with certain risk factors. Previously, the broad recommendation for PCV shots was for those older than 65.

“ACIP’s vote to expand adult pneumococcal vaccination to now include all adults aged 50 and older marks an important milestone in Pfizer’s long-standing commitment to reducing the burden of this life threatening disease,” Pfizer’s chief medical affairs officer for global vaccines and antivirals, Luis Jodar, Ph.D., said in a company release.

Merck, too is "pleased" with the vote, a company spokesperson said in an emailed statement. 

"This recommendation to lower the age-based recommendation is a significant step forward in efforts to enhance equitable access to pneumococcal conjugate vaccines and may improve vaccination rates," Merck's spokesperson added.

An age-based recommendation is more likely to boost uptake than a risk-based recommendation, the CDC’s pneumococcal vaccines work group pointed out in its presentation (PDF) to the committee. The expert panel also cited factors such as economic considerations, serotype coverage and health equity benefits to back its conclusion.

Pfizer’s Prevnar 20 is a next-generation follow up to its more limited Prevnar 13 and competes with Merck’s Capvaxive, a newer option that scored FDA approval in June.

Although Merck’s vaccine, like Pfizer’s, is approved for use in people at least 18 years of age, Capvaxive is the only pneumococcal disease vaccine that was specifically made to protect adults aged 50 and older. The 21 serotypes the vaccine contains account for 84% of the pneumococcal disease found in that population.

The 20 serotypes included in Prevnar 20, meanwhile, made up 50% of cases in the 50-64 years old age group between 2018 and 2022, according to Pfizer.

With the recommendation, which is pending final approval from the director of the CDC and the Department of Health and Human Services, the two vaccine options are once again on an even playing field. Still, analysts at Leerink Partners expect Capvaxine to snag the lion’s share of the adult market due to its higher disease coverage and better cost-effectiveness ratio, the team wrote in a note to clients. 

Merck could pick up $700 million incremental U.S. revenue in 2026 based on the new recommendation, the analysts added. 

However, Merck's dominance will likely be "short lived" due to upcoming competition with Vaxcyte’s 31-serotype candidate, according to Leerink analysts. 

Last month, head-to-head data from a phase 1/2 study pitting Vaxcyte’s VAX-31 against Prevnar 20 prompted Leerink analysts at the time to foresee a “strong likelihood” that the candidate could take majority market share in 2030.