Safety of concomitant administration of 23-valent polysaccharide pneumococcal vaccine and influenza vaccine among the elderly.

BACKGROUND: The current recommendation for the elderly is to receive both a single dose 23-valent pneumococcal polysaccharide vaccine (PPSV-23) and an annual inactivated influenza vaccine. There is a lack of post-marketing safety studies on concomitant vaccination using real-world data. We aimed to evaluate the safety of administering PPSV-23 and influenza vaccine concomitantly versus sequentially. METHODS: We performed a retrospective cohort study using a linked database that combines vaccination registry from the Korea Disease Control and Prevention Agency and claims data from the National Health Insurance Service. The study population included all those aged over 65 who received PPSV-23 at least once from Jan 1, 2016, to Dec 31, 2020. This study evaluated the 16 prespecified events of interest. Concomitant vaccination was defined as receiving both PPSV-23 and influenza vaccine on the same day. For sequential vaccination, we defined it as receiving influenza vaccination during the period from 30 to 365 days prior to the date of PPSV-23 injection. We performed 1:4 propensity score matching and estimated adjusted incidence rate ratio (aIRR) with a 95 % confidence interval (CI) using conditional Poisson regression. RESULTS: Of the 2,885,144 elderly patients who received PPSV-23 vaccination at least once from Jan 1, 2016, to Dec 31, 2020, a total 87,899 were included in the concomitant vaccination group and 1,200,091 were included in the sequential vaccination group. After adjusting for confounders, the concomitant group exhibited a significantly lower risk of allergic reactions (aIRR: 0.71, 95 % CI: 0.58-0.87), neuritis (aIRR: 0.72, 95 % CI: 0.57-0.91), and pneumonia (aIRR: 0.85, 95 % CI: 0.80-0.90), while demonstrating significantly higher risks of paralysis (aIRR: 1.63, 95 % CI: 1.05-2.52) compared to the sequential group. CONCLUSIONS: Concomitant administration of PPSV-23 and influenza vaccine in the elderly was not associated with a higher risk of most prespecified adverse events (AEs) compared to sequential vaccination. This study supports the safety of concomitant administration of PPSV-23 and influenza vaccine.

Effectiveness of COVID-19 vaccines against severe outcomes in cancer patients: Real-world evidence from self-controlled risk interval and retrospective cohort studies.

BACKGROUND: The effectiveness of COVID-19 vaccines is generally reduced in cancer patients compared to the general population. However, there are only a few studies that compare the relative risk of breakthrough infections and severe COVID-19 outcomes in fully vaccinated cancer patients versus their unvaccinated counterparts. METHODS: To assess the effectiveness of COVID-19 vaccines in cancer patients, we employed (1) a self-controlled risk interval (SCRI) design, and (2) a retrospective matched cohort design. A SCRI design was used to compare the risk of breakthrough infection in vaccinated cancer patients during the period immediately following vaccination ("control window") and the period in which immunity is achieved ("exposure windows"). The retrospective matched cohort design was used to compare the risk of severe COVID-19 outcomes between vaccinated and unvaccinated cancer patients. For both studies, data were extracted from the Korea Disease Control and Prevention Agency-COVID-19-National Health Insurance Service cohort, including demographics, medical history, and vaccination records of all individuals confirmed with COVID-19. We used conditional Poisson regression to calculate the incidence rate ratio (IRR) for breakthrough infection and Cox regression to estimate the hazard ratio (HR) for severe outcomes. RESULTS: Of 14,448 cancer patients diagnosed with COVID-19 between October 2020 and December 2021, a total of 217 and 3996 cancer patients were included in the SCRI and cohort study respectively. While the risk of breakthrough infections, measured by the incidence rate in the control and exposure windows, did not show statistically significant difference in vaccinated cancer patients (IRR=0.88, 95% CI: 0.64-1.22), the risk of severe COVID-19 outcomes was significantly lower in vaccinated cancer patients compared to those unvaccinated (HR=0.27, 95% CI: 0.22-0.34). CONCLUSION: COVID-19 vaccines significantly reduce the risk of severe outcomes in cancer patients, though their efficacy against breakthrough infections is less evident.