Why Not a Single Shot for All Influenza
Wednesday, August 26, 2009 at 11:08 AM EDT
Two different influenza
vaccines will be available in the fall of 2009. One will be a trivalent
preparation comprising seasonal influenza H3N2 and H1N1 strains, plus an
influenza B virus strain. A monovalent vaccine will also be available against
the 2009 pandemic H1N1 strain. Many readers of virology blog have asked why
these four virus strains will not be combined into a single, tetravalent
formulation. I posed this question to Dr. Ruben Donis, chief of the molecular virology and
vaccines branch at the U.S. Centers for Disease Control and Prevention. Here is
Some of the reasons that make tetravalent influenza vaccine less
attractive at this time:
- Regulatory considerations: there have been no clinical trials with
tetravalent influenza vaccines, and there is little time to do them now.
Licensing without data is not a favored option. However, clinical trials for a
monovalent have been started and will help establish appropriate doses,
formulations, in different population groups.
- Public health considerations: the populations at greater risk of severe
outcomes are not the same for the seasonal viruses and the H1N1 â€“
pregnant women are high on the list for receiving H1N1 vaccine.
- Timing considerations: Seasonal vaccine will be available in September
whereas pandemic H1N1 vaccine will become available later.
- Vaccine effectiveness, adverse events, pharmacovigilance: it will be easier
to monitor vaccine performance characteristics using a monovalent
He also mentioned the possiblity of making a trivalent preparation with the
pandemic H1N1 strain. But he said that
â€¦a trivalent with pandemic H1N1 would entail eliminating
one of the current seasonal viruses â€“ we donâ€™t have evidence that
any of the three seasonal viruses is becoming extinct.
I thank Dr. Donis for responding.
This article originally appeared on virology blog.