Cell-based flu vaccine could be more effective in preventing the flu

Abstract

A new retrospective analysis by Divino and colleagues published in the January 2022 issue of Open Forum Infectious Diseases found that cell-derived quadrivalent influenza vaccines (IIV4c) are significantly more effective than standard egg-derived quadrivalent influenza vaccines (IIV4e) at preventing influenza-related hospitalizations or ED visits, which is also associated with lower overall health care costs. Most influenza vaccines in the United States are manufactured using a traditional egg-based process, which is the standard of care and plays a critical role in influenza prevention. Based on the study’s initial sample of recipients, 79.3% (6,578,855 out of 8,300,292) of the study participants received IIV4e, while 20.7% (1,721,437 out of 8,300,292) received IIV4c during the study period of August 2019 to January 2020. “The IIV4e process can cause the influenza strain to mutate, which may lead to an antigenic mismatch between the circulating strains and the inactivated strains contained within the seasonal influenza vaccine,” said Victoria Divino, the study’s lead investigator. “This can result in reduced vaccine effectiveness, particularly for influenza A(H3N2) viruses.” The study used the IQVIA PharMetrics Plus administrative claims database to investigate influenza-related hospitalizations or ED visits and other clinical outcomes postvaccination classified by diagnosis codes during the 2019–2020 influenza season (beginning August 4, 2019, and ending March 7, 2020). Inverse probability of treatment weighting (IPTW)–weighted multivariate Poisson regression models were developed to estimate adjusted rate ratios (RRs) for IIV4c compared to IIV4e to estimate the adjusted average treatment effect, or the effect of treatment in the entire study population. Adjusted rVE was calculated as (1-RR)*100%. After applying eligibility criteria and IPTW adjustment, 1,150,134 and 3,924,819 participants aged 4 to 64 years received IIV4c and IIV4e, respectively. Comorbidities were evaluated at baseline, and vaccine cohorts were well-balanced on all measured confounders post-IPTW, including baseline comorbidity, said Divino, who is an associate principal at IQVIA, a data science company in Durham, NC. Clinical outcomes and all-cause costs were evaluated separately in this study post-IPTW. Divino and colleague’s study results demonstrate that IIV4c was significantly more effective than IIV4e in preventing influenza-related hospitalizations or ED visits, with an adjusted relative vaccine effectiveness (rVE) of 5.3% during a high influenza activity period between December 8, 2019, and March 7, 2020. Adjusted rVE was significantly higher for IIV4c in preventing hospitalizations/ED visits concerning any respiratory event (8.2%), pneumonia (6.7%), or asthma/COPD/bronchial events (7.6%), according to the study. IIV4c was also associated with significantly lower annualized all-cause costs postvaccination—with a difference of $467 per participant—than IIV4e, which Divino said is driven by lower costs for outpatient medical services and inpatient hospitalizations. Although IPTW was used to adjust for imbalances in measured confounders between the cohorts, which were well-balanced post-IPTW, it is possible that imbalances remained due to potential unmeasured confounding variables, according to Divino. “Unfortunately, the utilized database does not include information on socioeconomic status, race, or culture,” said Divino. “Also, the study sample was largely commercially insured or self-insured, so these findings may not be representative of the uninsured or Medicaid populations,” Divino noted, indicating that additional research is needed among uninsured and Medicaid populations. Given a choice between IIV4c and IIV4e influenza vaccine options, the findings demonstrate that the adjusted rVE of IIV4c is significantly better than that of IIV4e in preventing influenza-related hospitalizations/ED visits. IIV4c is also associated with significant cost savings.