Pfizer's Experimental Pneumococcal Vaccine Shows Stronger Immune Response Than Prevnar 20

Written By :  sheeba farhat
Published On 2026-05-20 18:05 GMT   |   Update On 2026-05-20 18:05 GMT
Pfizer

Bengaluru: Pfizer said on Wednesday its experimental pneumococcal vaccine showed ​significantly stronger immune response ​than its current shot, including up to ​15-fold higher antibody levels against a key strain, in a mid-stage study.

The vaccine maker tested its 25-valent vaccine, called 25vPnC, in healthy infants in the ‌trial.

Pneumococcal disease ⁠can ⁠cause infections in several parts of the body, including the lungs, ​raising the risk of pneumonia.

In the trial, the vaccine generated strong ​immune responses across all the strains it targets, and was well tolerated, with no safety concerns identified.

Antibody levels in patients ​after the third dose of 25vPnC were ⁠about 8.8 ‌times higher than those seen in Pfizer's ​Prevnar 20 ​and about 15 times higher after the ⁠fourth dose, the company said.

Prevnar 20 was first approved ​to prevent pneumococcal disease in the U.S. in ​2021 for adults, with its use later expanded to infants and children in 2023.

Pfizer said 25vPnC could potentially protect against about 90% of disease-causing strains in children under five, compared to current shots.

Based on the results and talks with regulators, the company has started a late-stage trial to test 25vPnC in up ​to 2,400 infants, comparing it with Prevnar 20 in a four-dose schedule.

Separately, Pfizer said it is advancing an adult pneumococcal vaccine candidate targeting 35 strains, with plans to begin clinical development by the end of 2026.

Children younger than 5 years and ‌adults aged 50 years or older are at higher risk of pneumococcal disease, according to the ​U.S. Centers ​for Disease Control ⁠and Prevention.

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