ATLANTA – (IPD) caused by PCV13 vaccine serotypes in adults aged 65 years and older, according to a case-control study involving Medicare beneficiaries.
Sharon Worcester/MDedge News
Olivia Almendares
Conversely, the 23-valent pneumococcal polysaccharide vaccine (PPSV23) showed limited effectiveness against serotypes unique to that vaccine in the study, which included 699 cases and more than 10,000 controls, Olivia Almendares, an epidemiologist at the Centers for Disease Control and Prevention, Atlanta, and her colleagues reported in a poster at the International Conference on Emerging Infectious Diseases.
“Vaccine efficacy against PCV13 [plus 6C type, which has cross-reactivity with serotype 6A] was 47% in those who received PCV13 vaccine only,” Ms. Almendares said in an interview, noting that efficacy was 26% against serotype 3 and 67% against other PCV13 serotypes (plus 6C). “Vaccine efficacy against PPSV23-unique types was 36% for those who received only PPSV23.”
Neither vaccine showed effectiveness against serotypes not included in the respective vaccines, she said.
The findings are timely given that the Advisory Committee on Immunization Practices (ACIP) is reevaluating its PCV13 recommendation for adults aged 65 years and older, she added.
“Specifically, ACIP is addressing whether PCV13 should be recommended routinely for all immunocompetent adults aged 65 and older given sustained indirect effects,” she said, explaining that, in 2014 when ACIP recommended routine use of the vaccine in series with PPSV23 for adults aged 65 years and older, the committee recognized that herd immunity effects from PCV13 use in children might eventually limit the utility of this recommendation, and therefore it proposed reevaluation and revision as needed after 4 years.
For the current study, she and her colleagues linked IPD cases in persons aged 65 years and older, which were identified through Active Bacterial Core surveillance during 2015-2016, to records for Centers for Medicare & Medicaid Services (CMS) beneficiaries. Vaccination and medical histories were obtained through medical records, and vaccine effectiveness was estimated as one minus the odds ratio for vaccination with PCV13 only or PPSV23 only versus neither vaccine using conditional logistic regression, with adjustment for sex and underlying medical conditions.
Of 2,246 IPD cases, 1,017 (45%) were matched to Medicare beneficiaries, and 699 were included in the analysis after those with noncontinuous enrollment in Medicare, long-term care residence, and missing census tract data were excluded. The cases were matched based on age, census tract of residence, and length of Medicare enrollment to 10,152 matched controls identified through CMS.
IPD associated with PCV13 (plus type 6C) accounted for 164 (23% of cases), of which 88 (12% of cases) involved serotype 3, and invasive pneumococcal disease associated with PPSV23 accounted for 350 cases (50%), she said.
PCV13 vaccine was given alone in 14% and 18% of cases and controls, respectively; PPSV23 alone was given in 22% and 21% of case patients and controls, respectively; and both vaccines were given in 8% of cases and controls.
Compared with controls, case patients were more likely to be of nonwhite race (16% vs. 11%), to have more than one chronic medical condition (88% vs. 58%), and to have one or more immunocompromising conditions (54% vs. 32%), she and her colleagues reported.
“PCV13 showed moderate overall effectiveness in preventing IPD caused by PCV13 (including 6C), but effectiveness may be lower for serotype 3 than for other PCV13 types,” she said.
“These results are in agreement with those from CAPiTA – a large clinical trial conducted in the Netherlands, which showed PCV13 to be effective against IPD caused by vaccine serotypes among community-dwelling adults aged 65 and older,” she noted. “Additionally, data from CDC surveillance suggest that PCV13-serotype [invasive pneumococcal disease] among children and adults aged 65 and older has declined dramatically following PCV13 introduction for children in 2010, as predicted.”
In fact, among adults aged 65 years and older, PCV13-serotype invasive pneumococcal disease declined by 40% after the vaccine was introduced in children. This corresponds to a change in the annual PCV13-serotype incidence from 14 cases per 100,000 population in 2010 to five cases per 100,000 population in 2014, she said; she added that IPD incidence plateaued in 2014-2016 with vaccine serotypes contributing to a small proportion of overall IPD burden among adults aged 65 years and older.
Increased pneumococcus immunity is important
ACIP’s reevaluation of the PCV13 recommendation is ongoing and will be addressed at upcoming meetings.
“As part of the review process, we look at changes in disease incidence focusing primarily on invasive pneumococcal disease and noninvasive pneumonia, vaccine efficacy and effectiveness, and vaccine safety,” she said. She noted that ACIP currently has no plans to consider revising PCV13 recommendations for adults who have immunocompromising conditions, for whom PCV13 has been recommended since 2012.
Ms. Almendares reported having no disclosures.
SOURCE: Almendares O et al. ICEID 2018, Board 376.