PCV13 serotypes still contribute to pneumococcal disease

Sheldon Kaplan, MD

The 13-valent pneumococcal conjugate vaccine (PCV13), approved for use in the United States in 2010, has substantially decreased the burden of disease from some forms of pneumococcal bacteria, but nearly a quarter of US pediatric cases are still caused by the strains covered by the vaccine. The PCV vaccine protects against just 13 of the more than 90 serotypes of pneumococcal bacteria that can cause disease, according to the new report.

The new study published in Pediatrics points out that invasive pneumococcal disease (IPD) in children has dropped since routine administration of the pneumococcal conjugate vaccine (PCV7) began in 2000, followed by the administration of a 13-valent pneumococcal conjugate vaccine-covering serotypes 1, 3, 4, 5, 6A, 6B, 7F, 9V, 14, 18C, 19A, 19F, and 23F-in 2010.¹ A 23-valent vaccine is also available for children aged 24 months to 18 years with specific underlying conditions, but most of predominant serotypes found in IPD cases in children are covered by the PCV-13 vaccine.

Despite the success of the vaccine, however, researchers have noted that there have been some cases described around the world in which children have developed IPD due to PCV13 serotype isolates despite having received at least 2 doses of the vaccine. Serotypes 3 and 19A were the most common in these cases and did not occur in children in the United States, according to the report. The children who did develop IPD from these serotype isolates often did not have immune evaluations completed or had normal immune workups, the report notes.

What researchers found

The study evaluated children with IPD at 8 US hospitals between 2014 and 2017 and found that PCV13 serotypes accounted for 23.9% of the IPD isolates during that period. Serotypes 3, 19A, and 19F made up 91% of these cases, with the most common non-PCV13 serotypes being 35B, 23B, 33F, and 22F. The study notes that 40% of the children with IPD from serotype isolates found in the PCV13 vaccine received only 1 or no doses of the vaccine. The research team concluded that PCV13 serotypes continue to account for nearly a quarter of IPD cases in children aged 4 to 7 years, even years after the introduction of the PCV13 vaccine.

Sheldon Kaplan, MD, professor and executive vice chair, and head of the Section of Infectious Diseases in the Department of Pediatrics at Baylor College of Medicine, Houston, Texas, and chief of the Infectious Disease Service and head of Pediatric Medicine at Texas Children’s Hospital, Houston. led the study and says although the vaccine is clearly effective in preventing IPD due to most serotypes in the PCV13 vaccine, there is still more work to be done.

“Since the introduction of PCV13, about 75% of pneumococcal isolates causing IPD were non-PCV13 serotypes. Of those children with non-PCV13 serotype IPD, more than half have some underlying condition compared with about 25% of children with IPD due to a PCV13 serotype isolate having an underlying condition,” Kaplan says. “IPD due to serotype 3 remains a challenge for prevention.”

Key takeaways

Kaplan says the report emphasizes how well PCV13 prevents IPD for most of the serotypes-with the exception of serotype 3-in the vaccine. He says that he hopes his research will help inform selection of pneumococcal serotypes for the next generation of PCVs, and that it also provides data regarding the utility of routine immune evaluations for children who have received 2 or more doses and still have an IPD episode due to 1 or more of the isolates found in the vaccine.

Kaplan says he had expected immune evaluations for children with IPD from the PCV13 serotypes, despite having received 3 or 4 doses of the vaccine, would have uncovered more potential immune abnormalities. According to the report, of the 28 children with IPD who had received 3 or more doses of the vaccine, just 1 was found to have an immunodeficiency.

Kaplan says the study, despite finding weaknesses in the vaccine pertaining to serotype 3, should highlight the importance of all routine vaccination-especially with PCV13.

“As they have been doing, pediatricians need to follow the recommended CDC-AAP-AAFP vaccine schedule for infants and children,” Kaplan says. “Pediatricians need to continue to educate the parents of their patients about the importance of having their children immunized against vaccine-preventable infections and following the recommended vaccine schedule. Parents need to know that Streptococcus pneumoniae can cause infections that are potentially fatal or lead to terrible brain injuries and/or deafness.”

References:

1. Kaplan SL, Barson WJ, Lin PL, et al. Invasive pneumococcal disease in children’s hospitals; 2014–2017. Pediatrics. 2019;144(3):e20190567.