Key Takeaways
1. Comparing PCV13 and PCV15 Vaccines: A recent study analyzed the antibody responses of adult participants (aged 18 to 49 years) who received either the pneumococcal 13-valent conjugate (PCV13) or pneumococcal 15-valent conjugate (PCV15) vaccines. These vaccines target common pneumococcal disease-causing serotypes—including conditions such as meningitis, sepsis, and non-bacteremic pneumonia—particularly in infants, children under 5 years of age, and adults over 50 years of age.
2. Similar Antibody Responses for Serotype 3: The study found that both PCV13 and PCV15 vaccines resulted in similar antibody responses to serotype 3. In addition, the immunoglobulin G concentrations for serotype 3 were comparable in both groups, and after vaccination, the concentrations had increased significantly in both vaccine groups.
3. Comparative Findings to Prior Research: This research aligns with prior studies that have compared PCV15 with PCV13 in older age groups. Similar trends in immunogenicity were observed, with increased IgG levels and opsonophagocytic activity antibody responses in both vaccine groups for shared serotypes.
Pneumococcal conjugate vaccines, including pneumococcal 13-valent conjugate (PVC13; Prevnar 13; Wyeth Pharmaceuticals, Inc.) and pneumococcal 15-valent conjugate (PVC15; vaxneuvance; Merck Sharp & Dohme Corp.), effectively target the capsular polysaccharides of the most common pneumococcal disease-causing serotypes. The morbidity and mortality of pneumococcal diseases (eg, meningitis, sepsis, non-bacteremic pneumonia) is high, particularly in infants and children 5 years of age and younger and adults 50 years of age and older.
A study published in Vaccine analyzed and compared the antibody responses to the 13 shared serotypes and functional opsonophagocytic activity (OPA) responses to serotype 3 in health participants who received PCV13 and PCV15 vaccines. The study analyzed results from a multicenter, randomized, open-label, active-control, phase 1 trial that evaluated the safety and immunogenicity of pneumococcal conjugate formulations.
Immunoglobulin G (IgG) concentrations of the 13 shared serotypes (1, 3, 4, 5, 6A, 6B, 7F, 9V, 14, 18C, 19A, 19F, and 23F) and serotype 3-specific OPA titers were analyzed before and 1 month (28 to 42 days) after vaccination. Functional serum antibody titers for serotype 3 were measured using a validated serotype-specific OPA assessment, and serum concentrations of serotype-specific anti-capsular IgG was determined by a validated Luminex-based direct immunoassay (dLIA) and expressed as µg/mL of serum.
A total of 87 adult participants, aged 18 through 49 years (mean age 35.6 years), were randomized to receive either PCV13 or PCV15. Participants were considered to be generally healthy with a stable pre-existing disease that didn’t require significant changes in therapy or who were hospitalized for worsening disease within 12 weeks before enrollment. Of the 87 participants, 46 received PCV13 and 41 received PCV15.
The results demonstrated that PCV13 and PCV15 vaccination promoted similar antibody responses to serotype 3. Prior to vaccination, the pneumococcal serotype 3 IgG concentrations were similar for the PCV13 group (geometric mean concentration [GMC] = 0.10 µg/mL [0.06, 0.15]) and the PCV15 group (GMC = 0.08 µg/mL [0.06, 0.11]).
The IgG concentrations in the 13 serotypes had increased after vaccination, and the serotype 3 IgG GMCs were 0.66 µg/mL [0.46, 0.94] and 0.76 µg/mL [0.52, 1.13] in the PCV13 group and PCV15 group, respectively. Further, the IgG geometric mean fold rises (GMFRs) for serotype 3 from before vaccination to 1 month after were 7.4 [4.8, 11.2] in the PCV13 group and 9.4 [6.3, 14.0] in the PCV15 group.
Further, pneumococcal serotype 3 OPA GMTs were similar in both groups prior to vaccine administration, and after 1 month, were 62.9 [48.9, 80.9] and 71.1 [50.9, 99.2] for PCV13 and blank for PCV15, respectively. In addition, the number of participants with a fold rise greater than or equal to 4 in serotype 3 OPA titers from before vaccination to 1 month after were 73.3% [58.1%, 85.4%] for PCV13 and 75.6% [59.7%, 87.6%] for PCV15.
A prior study that compared the immunogenicity of PCV15 with PCV13 in adults aged 65 years of age or older that were previously vaccinated with the 23-valent pneumococcal polysaccharide vaccine demonstrated similar trends in immunogenicity. Following vaccination, IgG levels and OPA antibodies had increased and were comparable across the 2 PCV vaccination groups for the shared serotypes, including serotype 3. Compared to the results of the current study, additional prior research conducted in different age groups (infants and adults >50 years of age) have found higher immune responses to serotype 3 with the PCV15 vaccine compared to PCV13.
A limitation of this study is the difference in participants’ ages compared to prior research, which included adults older than 49 years of age. Further, previous studies had compared PCV20 to PCV13, and the current study did not take PCV20 into consideration.
The authors note that although the serotype-specific OPA GMT and IgG GMC levels were variable between PCV13 and PCV15, the clinical significance of the differences are unknown because no serotype-specific corelate of protection against pneumococcal disease has been established in adults. Current evidence suggests that PCV13 stimulates an immune response that is sufficient to provide direct, individual-level protection against serotype 3 pneumococcal disease, according to the study authors.
Reference
Kanevsky I, Surendran N, McElwee K, et al. Comparison of pneumococcal immunogenicity elicited by the PCV13 and PCV15 vaccines in adults 18 through 49 years of age. Vaccine. 2023;41(45):6625-6629. doi:10.1016/j.vaccine.2023.09.043
