While the 13-valent pneumococcal conjugate vaccine (PCV13) for adults has been shown to reduce serious cases leading to hospitalization, the effect of vaccination on outpatient cases has not been clear.

A report in Clinical Microbiology & Infection discusses the efficacy of PCV13 in adults to prevent community-acquired pneumonia (CAP) and lower respiratory tract infections (LRTI) not requiring hospitalization.

Antibiotic prescriptions in primary care was one indicator used by in the University Medical Center Utrecht–led study.

“Pneumococcal conjugate vaccines (PCVs) have been available since 2000 and their introduction in infant immunization programs has reduced incidences of Invasive Pneumococcal Disease in non-immunized populations by 15-50%, with presumably similar relative incidence reductions of non-bacteremic pneumococcal pneumonia,” the Dutch researchers write.

“In the elderly, efficacy of the 13-valent PCV (PCV13) has been demonstrated for vaccine-type pneumococcal CAP and Invasive Pneumococcal Disease requiring hospitalization. It has been postulated that PCV13 also reduces the incidence of these episodes and associated antibiotic use in primary care,” they add.

To determine if that is the case, the study team randomized community-dwelling immunocompetent adults older than age 65 years to PCV13 or placebo as part of the double-blind Community-Acquired Pneumonia immunization Trial in Adults. Researchers extracted data on CAP and LRTI episodes and antibiotic prescriptions  from general practitioner information systems for 40,426 subjects in order to determine vaccine effectiveness (VE).

With 20,195 participants receiving PCV13 and 20,231 getting placebo, 1,564 and 1,659 CAP episodes occurred in the PCV13 and placebo group, respectively; VE (95% CI) was 5.5% (-2.6%–13.0%). At the same time, non-CAP LRTI episodes occurred 7,535 and 7,817 times in the PCV13 and placebo groups, respectively; VE (95% CI) was 3.4% (-2.0%–8.5%). 

In response, 8,835 and 9,245 LRTI-related antibiotic courses were prescribed in the PCV13 and placebo arms, respectively; VE (95% CI) was 4.2% (-1.0%– 9.1%). Researchers point out that antibiotic courses for any indication were prescribed 43,386 and 43,309 times, respectively; VE (95% CI) was -0.4% (-4.9%–3.9%).

“PCV13 vaccination in the elderly is unlikely to cause a relevant reduction in the incidence of CAP, LRTI, LRTI-related antibiotic use or total antibiotic use in primary care,” the authors conclude.

“Although the reductions of CAP and LRTI, if at all present, are likely to be small, the high incidence of these infections in primary care results in a much larger number of prevented cases as compared to the number of prevented hospitalized CAP cases,” the researchers explain. “However, costs and disease burden of CAP and LRTI treated in primary care is relatively low as demonstrated in a previous cost-effectiveness analysis.”

Therefore, the researchers advise, “prevention of CAP and LRTI episodes in primary care, although much more frequent as compared to other preventable pneumococcal disease, does not drive the societal value of pneumococcal vaccination in elderly.”
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