Pneumococcal Vaccine Protects More Than Just Kids Who Get It

Daniel M. Keller, PhD

October 14, 2014

PHILADELPHIA — The use of PCV13, a 13-valent pneumococcal conjugate vaccine (Prevnar13, Pfizer), in children has dramatically reduced the incidence of invasive pneumococcal disease in children and adults, according to a recent study.

"When we looked at the strains that are only in PCV13, we found a 93% reduction in disease in children younger than 5 years by 2012/13," said Lindsay Kim, MD, from the National Center for Immunization and Respiratory Diseases at the Centers for Disease Control and Prevention (CDC) in Atlanta.

PCV13 was introduced in 2010 and covers five strains of pneumococcus (1, 3, 5, 7F, 19A) not contained in the earlier 7-valent vaccine (PCV7). PCV13 has been recommended for children at 2, 4, 6, and 12 to 15 months of age. for protection against pneumococcal disease, but disease has also been prevented in adults.

"What's happening is that the vaccine actually reduces the transmission between persons. If we immunize the children, it reduces the transmission between children and other children and adults," Dr Kim told Medscape Medical News.

She presented the study results here at IDWeek 2014.

Dr Kim and colleagues estimated the number of cases prevented with PCV13 by comparing the number of observed cases of pneumococcus with the number expected without PCV13. They used time-series models that accounted for seasonality and pre-PCV13 trends.

All cases isolated from a normally sterile site were accrued from the Department of Health and Human Services Active Bacterial Core Surveillance of invasive bacterial pathogens of public health importance and confirmed with laboratory testing.

The number of cases of invasive pneumococcal disease caused by the newly covered serotypes fell rapidly in the first season after the introduction of PCV13, 2010/11, and continued to decline in all age groups in subsequent years.

Table. Change in Incidence of Pneumococcal Disease After PCV13

Age Group (Years) 2010/11, % 2011/12, % 2012/13, %
<5 –66 –88 –93
5–17 –33 –59 –75
18–49 –33 –64 –72
50–64 –23 –54 –62
≥65 –23 –46 –58

 

Of the 400,000 cases of invasive pneumococcal disease prevented in children and adults, 30,000 of those have happened in the 3 years since the introduction of PCV13, Dr Kim reported. And in the 3 years since the introduction of PCV13, about 30,000 of the cases prevented have been in adults, who never received the vaccine.

The declines were driven primarily by less serotype 19A and 7F disease. "It boils down to the fact that PCV13 is a really effective tool — it is the most effective tool — in decreasing the incidence of severe pneumococcal disease," she explained.

A few years after the introduction of PCV7, epidemiologists detected strain replacement, especially with serotype 19A, which is associated with antibiotic resistance. PCV13 includes that serotype, so 19A disease has been reduced. "We also found that antimicrobial resistance, overall, has been reduced in invasive pneumococcal disease," Dr Kim reported.

But, she added, it is impossible to predict whether a strain not covered by PCV13 will emerge in the future. In the 2012/13 season, there was a hint of potential serotype replacement in adults 50 to 64 years of age.

The emergence of nonvaccine strains might occur, but "I suspect not," said Andrew Pavia, MD, chief of pediatric infectious diseases and professor of pediatrics at the University of Utah in Salt Lake City.

"I think we're getting most of the marquee players," he told Medscape Medical News. "Most of the stars of the pneumococcal world are now targeted, so we're dealing with the second stringers." But he cautioned that this prediction is made "with a lot of hubris because it could be proven very wrong."

Pneumococcal vaccines might prevent noninvasive disease in addition to invasive disease. After the first pneumococcal conjugate vaccine was introduced, studies showed a moderate decrease in otitis media, Dr Pavia noted. "The smaller studies actually tapped ears and showed some decrease in the number of otitis media cases that were due to pneumococcus."

Earlier this year, results from the Community-Acquired Pneumonia Immunization Trial in Adults (CAPiTA) showed that PCV13 prevented noninvasive community-acquired pneumonia in adults 65 years and older. On the basis of those findings, Dr Kim said, the CDC Advisory Committee on Immunization Practices now recommends PCV13 for this age group, in addition to the 23-valent PPSV23 vaccine.

The study received no commercial finding. Dr Kim and Dr Pavia have disclosed no relevant financial relationships.

IDWeek 2014: Abstract 647. Presented October 10, 2014.

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