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During the past 20 years, rates of invasive pneumococcal disease among older U.S. adults (age, ≥65) have plummeted. Experts ascribe this trend entirely to beneficial effects of the conjugate vaccines given to children, which have greatly reduced carrier states and boosted herd immunity (NEJM JW Gen Med Aug 15 2019 and Clin Infect Dis 2019; 69:34). In the 5 years since the 13-valent conjugate vaccine (PCV13; Prevnar) was first recommended for all older adults, it has had no discernable further direct effect on risks for either invasive disease (i.e., bacteremic pneumonia or meningitis) or nonbacteremic pneumonia in this population. In fact, as is now the case in many countries, most pneumococcal disease in the U.S. is caused by serotypes not covered by the conjugate vaccine.
In June 2019, the CDC's Advisory Committee on Immunization Practices noted these trends and reconsidered its 2014 recommendation that all healthy older adults receive a dose of PCV13 (Branswell H. STATnews.com. June 26, 2019). Rather than continuing to endorse universal use of the vaccine, or reversing policy and advising against its use, the committee recommended that clinicians decide on their own whether or not to vaccinate, after a “shared clinical decision-making” process with their patients. This recommendation undoubtedly will soon become official CDC policy. A video of the committee's deliberations is freely available on YouTube and provides an immensely educational 90-minute lesson on both the complexities of modern pneumococcal epidemiology and the impressive difficulties of creating sensible health policy.
The standard metrics of public health suggest that PCV13 is an expensive and unnecessary intervention. The CDC estimates its price tag at between US$200,000 and >$500,000 per quality-adjusted life-year. The “number needed to vaccinate” to prevent 1 case of invasive pneumococcal disease is estimated to be 26,000 annually; the estimated number to prevent 1 case of pneumonia ranges from 2600 to 14000. For individuals, though, the vaccine's benefits are not dismissed so easily. It might well be lifesaving for an older adult who is challenged by a vaccine-type pneumococcus, especially one who does not fit the CDC's definition of “immunocompromised” but might still have difficulty clearing an infection caused by this sometimes-lethal organism. However, these rare cases of potential benefit are impossible to identify in advance.
The advisory committee ruefully noted the off-putting complexity of the current adult pneumococcal vaccine recommendations and its concern that making yet more drastic changes would be confusing, demoralizing, and burdensome for patients and providers (not to mention those in charge of the vaccine sections of the nation's electronic medical records.) Further, committee members fully sympathized with clinicians who are supposed to engage in “shared clinical decision making” without clear clinical signposts to guide them.
Assuming few clinicians will have the time or inclination to watch the entire committee discussion, some of its take-home points might help them help their patients:
The new policy is not intended to affect use of the older 23-valent vaccine (PPV23; Pneumovax), which still is recommended for all immunocompetent older adults (age, ≥65).
The new policy does not apply to immunocompromised patients, who should continue to receive PCV13 in series with PPV23.
PCV13 remains a safe vaccine, with no postmarketing concerns.
PCV13 might be a reasonable intervention for patients living in communities with higher-than-average incidence of pneumococcal disease; for those with diabetes or serious liver, lung, or heart disease; and for frail elders.
Patients' own risk calculations will (in theory) help clinicians make vaccination decisions. Still, once mundane considerations of cost and convenience have been addressed, the outcome of the shared decision-making process is predictable: Patients who embrace all medical interventions likely will opt for vaccination, and those who avoid whatever can be avoided likely will opt out. The rest will probably do whatever the clinician suggests.
Meanwhile, speaking of PPV23, what's in store for that old standby? The venerable polysaccharide vaccine generally is considered to be less immunogenic than conjugate vaccines, although it does address a broader spectrum of pneumococcal serotypes. PPV23 contains 12 of PCV13's serotypes, and, clearly, its public health metrics also have been affected by the rapidly changing landscape of pneumococcal disease, but they were not part of the June 2019 committee agenda. New pneumococcal conjugate vaccines are on the horizon, with almost as broad an array of serotypes as PPV23, and their availability likely will force specific reconsideration of PPV23's use in the near future.