Recently, Morbidity and Mortality Weekly Reports (MMWR): Recommendations and Reports published recommendations from the United States Centers for Disease Control and Prevention (CDC) Advisory Committee on Immunization Practices (ACIP) on the use of pneumococcal vaccines in adults in the United States.
Study: Pneumococcal Vaccine for Adults Aged ≥19 Years: Recommendations of the Advisory Committee on Immunization Practices, United States, 2023. Image Credit: JPC-PROD / Shutterstock.com
Occurrence and transmission of pneumococcal disease
Pneumococcus is a bacterial infection caused by Streptococcus pneumoniae or pneumococcus. This bacterium colonizes the upper respiratory tract of humans and can cause mild to severe infection.
Pneumococcus is primarily transmitted through the respiratory droplets of the infected person. Young children are a common reservoir of pneumococci as compared to adults, as they are more susceptible to the infection.
Older adults who live in nursing homes, are in close contact with children below six years of age, or smoke cigarettes are also at an increased risk of pneumococcus. Adults with underlying medical conditions such as chronic diseases associated with heart, lung, liver, and kidney, and diabetes are at an increased risk of developing severe pneumococcal infection.
A 2017 U.S.-based surveillance study of hospitalized non-bacteremic pneumococcal pneumonia (NBPP) revealed that the incidence rate of pneumococcal pneumonia was 12 for every 100,000 adults aged between 18 and 49 years of age and 105 for every 100,000 adults above 65 years of age.
A reduced incidence of pneumococcal disease was reported during the early phase of the ongoing coronavirus disease 2019 (COVID-19) pandemic. This reduction could be due to the implementation of nonpharmaceutical strategies that decreased the circulation of respiratory viruses, such as respiratory syncytial virus (RSV) and influenza. More recently, recent studies have indicated a rise in invasive pneumococcal disease (IPD) in Europe and the U.S. after the relaxation of non-pharmaceutical interventions.
Management of pneumococcal disease
Pneumococcal disease outbreaks have occurred in various settings including military training facilities, hospital wards, long-term care facilities, and correctional facilities.
The CDC does not have any recommendations for individuals exposed to a patient with pneumococcal disease; however, vaccination and antimicrobial chemoprophylaxis are used to limit bacterial transmission during outbreaks. Several preventive strategies, such as isolating the patient from the healthy group, proper respiratory hygiene, and restriction of patient movements are also commonly implemented.
A recent systematic review highlighted the effectiveness of several antibiotics, such as azithromycin, amoxicillin, penicillin G, and levofloxacin, to control pneumococcal disease outbreaks in closed settings. An individual immunized with vaccines containing the serotype of the circulating pneumococcus will be protected from the disease for a longer period as compared to those who receive antimicrobial chemoprophylaxis treatment.
Pneumococcal vaccines in adults
Prior to 2021, ACIP recommended a 23-valent pneumococcal polysaccharide vaccine (PPSV23) alone or in combination with the 13-valent pneumococcal conjugate vaccine (PCV13) for U.S. adults, depending on their age. In 2021, the U.S. Food and Drug Administration (FDA) approved the use of two new pneumococcal conjugate vaccines (PCVs) including PCV15 and PCV20 for individuals 18 years of age and older. At present, one PPSV and three PCVs are licensed and available for use in the U.S.
Both PPSV and PCV elicit immune responses in different ways. PCVs are more effective than PPSV23, as PCVs induce higher levels of serotype-specific immunoglobulin G (IgG).
Although administering PCVs in children significantly reduced the prevalence of PCV-type pneumococcal disease, the incidence of IPD did not decline between 2014 and 2019. Since 2014, PCV13 vaccination coverage has significantly increased in adults 65 years and older.
PCV15 and PCV20 are intramuscularly administered at a dose of 0.5 mL. In the event that PCV15 or PCV20 are not available, PCV13 is used.
The same dose of PPSV23 can be administered intramuscularly or subcutaneously. No significant differences in immunogenicity based on the route of administration have been observed.
PCV15, PCV20, and PPSV23 are currently available in a single-dose and prefilled syringe. At present, vaccine efficacy data is not available for PCV15 or PCV20. Vaccine doses vary in individuals with or without immunocompromised conditions.
The current ACIP recommendations have provided specific recommendations for the use of pneumococcal vaccines.
To this end, PCV20 or PCV15 can be used alone or in series with PPSV23 for all adults 65 years and older. These vaccines can also be used for adults between 19-64 years of age with underlying medical conditions at varied dosages.
Adults who start their pneumococcal vaccine series with PCV13 but do not receive all doses are recommended to receive a single dose of PCV20 or more than one dose of PPSV23.
Clinicians are advised to determine whether a supplemental PCV20 dose is required for adults above 65 years who completed the recommended vaccine series. The current report contains clinical guidance for adults who received 7-valent PCV (PCV7) only and for those who were hematopoietic stem cell transplant recipients.