Benefits now appear to have reached a plateau
• by Michael Smith, North American Correspondent, MedPage Today October 09, 2017

Action Points
• Note that this study was published as an abstract and presented at a conference. These data and conclusions should be considered to be preliminary until published in a peer-reviewed journal.
• Note that this epidemiologic study found that rates of invasive pneumococcal disease fell after the introduction of the 13-valent Pneumococcal Conjugate Vaccine.
• Be aware that non-vaccine serotype prevalence was relatively flat, implying these strains did not move into niches cleared by the vaccine.

SAN DIEGO — The 6 years after the 13-valent pneumococcal vaccine (Prevnar 13) was introduced saw a sustained drop in the rate in invasive pneumococcal disease (IPD) among children and adults, researchers reported here.
And analysis of surveillance data suggested that the 13 vaccine serotypes have not been replaced by others as causes of disease, according to Tamara Pilishvili, MPH, of the CDC’s National Center for Immunizations and Respiratory Diseases in Atlanta, and colleagues.
On the other hand, the decline in IPD has slowed and reached a plateau in the past 2 years, Pilishvili reported at the annual IDWeek meeting, sponsored jointly by the Infectious Diseases Society of America (IDSA), the Pediatric Infectious Diseases Society (PIDS), the Society for Healthcare Epidemiology of America (SHEA), and the HIV Medicine Association (HIVMA).
The pattern is much the same for pneumococcal meningitis, she said.
Vaccine expert Kathryn Edwards, MD, of Vanderbilt University School of Medicine in Nashville, who moderated the IDWeek session, lauded the “beautiful data” in the study. “It’s a continuing story,” she told MedPage Today, and the surveillance data “allows us to see” how well the vaccine is working.
For a pediatrician, “It’s wonderful to rarely see meningitis and the burden of bacterial pneumonia is much less” since the pneumococcal vaccines have been used, she noted.
When the drugs were being developed, some experts feared that preventing disease caused by the vaccine serotypes — only a handful of the more than 90 that exist — would simply lead to other serotypes stepping in to fill the gap.
“That doesn’t seem to have happened, but it’s fair to say that we need to continue to look at it,” Edwards stated.
The 13-valent vaccine was introduced in 2010 for children under age 5, but in 2014 the CDC’s Advisory Committee on Immunization Practices suggested it should also be used routinely by people ages 65 and up, in the wake of a European study that suggested they would benefit.
For this analysis, Pilishvili’s group looked at rates of IPD among children and seniors, using data from the Active Bacterial Core surveillance program from July 2007 through June 2016. They defined IPD as pneumococcus isolated from a normally sterile site.
They compared IPD rates in 2007-2008 — before the vaccine was introduced — with rates in 2016 for both children and seniors.
The comparisons showed that for children, the rate of IPD associated with the vaccine serotypes (plus serotype 6C, which is not in the vaccine but is cross-reactive with vaccine strains) fell 87% and the overall rate of IPD for all serotypes fell 61%.
Also, for seniors, the rate associated with vaccine serotypes and 6C fell 68%, while the overall rate fell 40%.
Finally, for both groups, there were no major changes in the rates of disease caused by non-vaccine serotypes.
One expected effect of vaccinating children was a herd immunity that would help protect older adults, who like children, are at risk from pneumococcal disease.
And, interestingly, most of the change in IPD rates among seniors occurred before 2014 (but after the children were being inoculated) and rates have been stable since then, suggesting there has been “no measurable early impact” of vaccine use by the older population, the researchers argued.
Before the vaccine was introduced for children, Pilishvili said, most IPD was caused by two serotypes, 19A and 07F. But data for 2016 shows that disease caused by 07F has almost disappeared and cases caused by 19A are a fraction of their earlier number.
A similar pattern was observed for seniors, although some disease caused by serotype 07F is still seen.
On the other hand, the vaccine serotype 003 is still causing disease in both groups and doesn’t seem to have been much affected by the medication, she noted.
“Further work is needed to explain reductions in non-vaccine type disease observed in the post-[Prevnar 13] era,” the authors concluded.

The study was supported by the CDC.
Pilishvili disclosed no relevant relationships with industry. Two co-authors disclosed relevant relationships with Pfizer, Merck, Novavax, Dynavax, Sanofi-pasteur, GlaxoSmithKline, and Seqirus.
Edwards disclosed a relevant relationships with Novartis.
• Reviewed by F. Perry Wilson, MD, MSCE Assistant Professor, Section of Nephrology, Yale School of Medicine and Dorothy Caputo, MA, BSN, RN, Nurse Planner
• Primary Source
IDWeek
Source Reference: Pilishvili T, et al “Direct and indirect impact of 13-valent pneumococcal conjugate vaccine (PCV13) on invasive pneumococcal disease (IPD) among children and adults in the U.S.” IDWeek 2017; Abstract 2492.