Two new studies with data from laboratory-confirmed influenza cases in children from seven major hospitals from 2016–2018 and adult data from FluServ-NET between 2013 and 2018 presented at IDWeek 2019 in Washington DC showed once again that seasonal influenza vaccines are effective.
Annual vaccinations reduced the number of hospitalisations in children by 50%, not only in patients with pre-existing conditions but also in healthy children (40% of the cases). In adults, influenza vaccination reduced the risk of severe influenza by 36%, showing that influenza vaccines can prevent hospitalisations and deaths.
During the Influenza Vaccine Symposium, Meagan Fitzpatrick from the University of Maryland presented data from the 2017–2018 US season, in which the influenza vaccine only had an effectiveness of 20% and a coverage of 43%, but nevertheless prevented nearly 62,000 deaths. Further, mathematical modelling showed that the influenza burden is actually more sensitive to changes in vaccination coverage than changes in vaccine efficiency, and the highest impact can be achieved by prioritizing school-age children and young adults.
This finding is in accordance with experts interviewed by GlobalData, emphasising that the need of high seasonal influenza vaccination rates is as important as more effective vaccines, and recommendations have to be extended to children worldwide.
Dr Fitzpatrick also presented modelling data showing that potential universal influenza vaccines with an efficacy of 75% would be able to reduce hospitalisation by 96%, but also that efficacy of 60% would significantly reduce the burden of seasonal influenza.
The forthcoming GlobalData report “Seasonal Influenza: Global Drug Forecast and Market Analysis to 2028” projects the US launch of universal influenza vaccines from Biondvax, Imutex, and FluGen by 2026, and a share of 18% by 2028 in the eight major markets.
Influenza challenge models can be an insightful tool to study influenza vaccines, as Matthew Memoli from the National Institute of Allergy and Infectious Diseases showed by giving the same virus strain to the same patients in subsequent years. While 50% of the study participants developed some immune response to the strain, the other half did not despite showing an infection. The data suggest that the influenza antigen included in most vaccines, the head of the hemagglutinin protein (HA), is not sufficient to elicit an immune response in all patients. Interestingly, neither were antigens from the HA stem, the target of many universal influenza vaccines, given to study participants in a Janssen study. Additionally, mutations in the HA stalk structure were observed. Rather, another influenza virus surface protein, neuraminidase (NA) was a better predictor of the severity of influenza infections. Dr Memoli furthermore showed clinical data from FLU-v, a universal T-cell vaccine candidate from Imutex that was able to reduce the rate of influenza infections with a single dose, showing that cellular immunity alone was able to provide protection.
For universal vaccine development, this means a combination of many different epitopes might be the best approach to reach protection against multiple strains, and also the importance to achieve both humoral and cellular immunity to broadly protect patients of different age groups and with different histories.
IDWeek is the joint annual meeting of the Infectious Diseases Society of America (IDSA), Society for Healthcare Epidemiology of America (SHEA), the HIV Medical Association (HIVMA), and the Pediatric Infectious Diseases Society (PIDS).
GlobalData (2019). Expert Insight: Newly Identified HA Binding Site Could Prove Useful for Universal Influenza Vaccine Development, May 2019, GDHC2445EI
GlobalData (2019). Expert Insight: Universal Influenza Vaccine Development Takes Front Seat in WHO’s Influenza Strategy, March 2019, GDHC2322EI
GlobalData (2019). Seasonal Influenza Vaccines: Global Forecast and Market Analysis to 2028, to be published