One dose of 2009 H1N1 vaccine will protect most pregnant women
Current preliminary evidence suggests that a single 15- or 30-mcg
dose provides strong immune response among healthy pregnant
women.
Because pregnant women have a higher risk of complications from
influenza virus and can potentially provide protection to infants who
cannot be vaccinated, they are among the priority groups identified by
CDC for receiving the 2009 H1N1 vaccine. CDC indicates that, since the
start of the 2009 H1N1 influenza outbreak, approximately 30 pregnant
women have died after becoming infected with the virus. Pregnant women
infected with the 2009 H1N1 influenza virus also have a higher rate of
hospitalization than the general population, with recent data showing
that at least 100 pregnant women with 2009 H1N1 infection have been
hospitalized in intensive care units in the United States.
Early results from an ongoing study sponsored by the National
Institute of Allergy and Infectious Diseases (NIAID), National
Institutes of Health, indicated that healthy pregnant women form a
robust immune response after one dose of 2009 H1N1 influenza vaccine.
Investigators reported that blood samples taken 21 days after
single-dose vaccination from a subgroup of 50 pregnant participants
showed the following:
- In 25 women receiving a single 15-mcg dose of the vaccine, the H1N1
influenza vaccine evoked an immune response that was likely to be
protective in 23 (92%) of these women.
- In 25 women receiving a single 30-mcg dose of the vaccine, the H1N1
flu vaccine evoked an immune response that was likely to be protective
in 24 (96%) of these women.
The trial began in early September and reached its target enrollment
(120 volunteers) in mid-October. All women in the study are between 18
and 39 years of age and were enrolled in their second or third trimester
(14–34 weeks) of pregnancy. Participants were randomized into two
groups: 60 are receiving two doses of a 15-mcg vaccine, and the other
half are receiving two doses of a 30-mcg vaccine. The two injectable
vaccine doses are being administered 3 weeks apart.
The vaccine has been well tolerated by participants, and no safety
concerns related to the vaccine have arisen thus far. The study
investigators and an independent safety-monitoring committee are
monitoring trial safety closely. Additional details regarding the design
of the study are available at this
ClinicalTrials.gov website.
CDC has recommended that pregnant women not receive the intranasal,
live attenuated H1N1 vaccine (LAIV), resulting in a difficult situation
when the first H1N1 vaccine doses became available because nearly all
doses were the LAIV version. However, now that about one-half of the
increasing vaccine supply consists of the injectable version, officials
expect that access to the vaccine by pregnant women and other high-risk
groups will be less of an issue.
The group recommended a single dose for all patients 10 years or
older, assuming vaccine use coincides with guidelines of national
regulatory authorities.
Sources
Related sources on pharmacist.com
Joe Sheffer (jsheffer@aphanet.org)
Posted November 9, 2009
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