December 19, 2018 (Center for Infectious Disease Research and Policy)
The last influenza season was a remarkably bad one, dominated by the H2N2 strain and hit senior citizens particularly hard.
A retrospective cohort study involving over 13 million Medicare beneficiaries who received an influenza vaccine during the 2017-2018 season found that vaccines that were cell-based performed better than vaccines that were egg-based.
A Poisson regression was used to assess these 13 million Medicare beneficiaries who were aged 65 and older. Five vaccine formulations were tested on this group during the 2017-2018 flu season. They were as follows:
- Flucelvax (made by Seqirus)
- Egg-based quadrivalent (four-strain)
- Egg-based high-dose
- Standard-dose vaccines
The last three listed are three-strain.*
Of those vaccinated until the end of January, 5 percent received cell-cultured quadrivalent, 14 percent received egg-based quadrivalent, 63 percent received high-dose, 11 percent received adjuvanted, and 7 percent received standard-dose trivalent.
Researchers paid close attention to the impact each of these vaccines had against the number of flu-related hospitalizations and emergency room visits as a way of determining performance.
For preventing flu hospitalization, inpatient stays, and clinic visits, cell-cultured vaccines’ effectiveness was approximately 10 to 11 percent higher than that of standard-dose egg-based quadrivalent vaccines.
Out of all five vaccines, relative vaccine effectiveness against hospitalizations and emergency visits was highest for cell-based (11 percent) and high-dose (9 percent) vaccines.
Although these differences exist, researchers say that this study does not rule out other factors that may explain these differences discovered. A slew of other factors could be to blame for these differences. The researchers agree, however, that lessons from these studies will help not only improve influenza vaccines, but also aid in vaccine strategies for optimizing protection for seasonal influenza vaccines.