Post-Marketing Surveillance Study Affirms Safety of Pneumococcal Vaccines

A post-marketing surveillance using the US Vaccine Adverse Event Reporting System (VAERS) database has affirmed the established safety profile of pneumococcal vaccines, with reporting indicating predominantly non-serious adverse events (AEs) and most AEs clustered within 30 days post-vaccination. The research, published in Frontiers in Cellular and Infection Microbiology, emphasizes the use of temporal risk patterns to guide monitoring protocols and risk-benefit evaluations post-vaccination.¹

VAERS and Pneumococcal Vaccines

Pneumococcal vaccines help prevent potentially serious and fatal invasive pneumococcal diseases (IPDs), which can encompass pneumonia and meningitis. The introduction of conjugate vaccines in the US provided at-risk populations a series of options to receive protection. Unfortunately, despite widespread implementation and marketing of pneumococcal vaccination programs, there remains a high incidence of IPD in the US. Most pertinently, the pathogen accounts for almost 300,000 annual deaths among children aged younger than 5 years.^1,2

The reporting of immunization-associated AEs remains important, even after approval. VAERS is a national passive surveillance system encompassing the US population, providing critical insights into pharmacovigilance of immunizations. The system enables nearly real-time detection of potential safety issues associated with vaccines, though these are self-reported incidents and not always grounded in truth. Still, these safety signals can provide important insights into possible concerns that can be investigated further in future research.^1,3

In the current analysis, investigators employed comprehensive data mining of VAERS reports regarding multiple pneumococcal vaccine formulations. They sought to describe post-pneumococcal vaccination safety profiles and establish an evidence-based risk stratification to help inform future vaccination strategies. For pharmacists, knowing the possible adverse events following pneumococcal vaccination can help inform patient counseling and preparation, helping to ease possible safety concerns and increase uptake.¹

Most AEs After Pneumococcal Vaccination are Mild and Transient

Reports to VAERS related to pneumococcal vaccines between January 1990 and March 2025 were analyzed. A total of 157,244 patients who received the pneumococcal vaccine with 632,481 AEs were documented. Regarding the clinical profile of AEs, for those experiencing AEs following vaccination, the most frequent clinical outcome was complete recovery (44.2%), followed by hospitalization attributable to the AEs (14.94%). A temporal analysis indicated that 77.11% patients developed AEs within 0 to 30 days post-vaccination.¹

There was a total of 158,778 doses of pneumococcal vaccines administered. Accordingly, VAERS reports documented 7740 pneumococcal vaccine-associated Preferred Term (PT) codes, which were utilized for standardized AE symptom documentation. The most frequent PTs for positive AE signals were injection site erythema, injection site swelling, injection site pain, erythema, and injection site warmth. Furthermore, the most frequent system organ classes (SOCs), used to classify AE regions, were general disorders and administration site conditions; investigations; skin and subcutaneous tissue disorders; nervous system disorders; and infections and infestations.¹

What Should Pharmacists Know?

To the knowledge of the investigators, the study was the first pharmacovigilance investigation to successfully integrate safety signals across multiple pneumococcal vaccines using VAERS reports. A disproportionality analysis found that pyrexia, injection site erythema, swelling, and pain were the most frequently reported AEs following pneumococcal vaccination. Importantly, most of these cases were non-severe, and were primary self-limited localized and systemic events mirroring observations in prior research.¹

Although the VAERS database has key strengths, including its nationwide coverage and ability for real-time reporting, it has inherent limitations regarding causality assessment and data granularity, “necessitating cautious interpretation of observed associations,” according to the investigators. Still, observations through VAERS can serve a use for pharmacists seeking to prepare themselves to counsel patients following pneumococcal vaccination. The AEs identified in this trial were all mild in nature, a key piece of information pharmacists can provide to patients in advance of vaccination.¹

Pharmacists can ensure they are reachable after a patient receives pneumococcal vaccination to discuss any potential AEs that appear. Patients should also be assured that, if necessary, they can return for in-person follow-up within the 30 days post-vaccination, as that time seemed to consist of the most AE occurrences. Overall, pharmacists remain a trusted health care provider in managing patient concerns regarding pneumococcal vaccination and are in a prime position to advocate for the benefits of vaccination.

REFERENCES

1. Zheng X, Liu M, Ding A, Zhang S, et al. Post-marketing safety surveillance of pneumococcal vaccines: a real-world pharmacovigilance study using the U.S. vaccine adverse event reporting system (VAERS) database. Front Cell Infect Microbiol. 2025;15. doi:10.3389/fcimb.2025.1635180

2. Iskander JK, Miller ER, Chen RT. The role of the Vaccine Adverse Event Reporting system (VAERS) in monitoring vaccine safety. Pediatr Ann. 2004;33(9):599-606. doi:10.3928/0090-4481-20040901-11

3. Wahl B, O’Brien KL, Greenbaum A, et al. Burden of Streptococcus pneumoniae and Haemophilus influenzae type b disease in children in the era of conjugate vaccines: global, regional, and national estimates for 2000-15. Lancet Glob Health. 2018;6(7):e744-e757. doi:10.1016/S2214-109X(18)30247-X