Novel H1N1 (swine) flu news
The following experts from the Center for Disease Control, William L. Atkinson, MD, MPH, and Andrew T. Kroger, MD, MPH, medical epidemiologists, at the National Center for Immunization and Respiratory Diseases, have answered the following questions about the new H1N1 flu vaccine as of early September 2009. The H1N1 is different from the seasonal flu which is different strain of influenza.
Q: When will vaccine for the 2009 H1N1 influenza virus be
available?
A: CDC estimates that approximately 45 million doses of H1N1
influenza vaccine will be available in mid-October. CDC
anticipates that approximately 20 million additional doses
will be released in each subsequent week. Keep in mind that
vaccine availability is driven by a number of variables in
the manufacturing process. Once vaccine is available,
vaccination should begin immediately.
Q: Is the 2009 H1N1 influenza vaccine experimental?
A: No. H1N1 influenza vaccine will be available in an
inactivated, injectable formulation and a nasal-spray, live
attenuated formulation. Neither is an experimental vaccine.
The 2009 H1N1 influenza vaccines are made employing the same
methods and facilities used annually to produce seasonal
influenza vaccine. The vaccines are undergoing additional
clinical trials at this time to determine the size of the
dose and the number of doses that will be needed for
protection.
Q: Once a 2009 H1N1 influenza vaccine becomes available, who
will be targeted to receive the vaccine?
A: On August 28, 2009, CDC issued recommendations for the
use of the 2009 H1N1 influenza vaccine. The recommendations
identify 5 initial target groups for H1N1 influenza
vaccination. They are (1) pregnant women; (2) people who
live with or provide care for infants younger than age 6
months (e.g., parents, siblings, day care providers); (3)
healthcare and emergency medical services personnel; (4)
children and young adults ages 6 months through 24 years;
and (5) people ages 25 through 64 years who have medical
conditions that put them at higher risk for influenza-
related complications. You can access the complete
recommendations at http://www.cdc.gov/mmwr/PDF/rr/rr5810.pdf
Q: Why are pregnant women prioritized for vaccination?
A: Data from early 2009 H1N1 influenza cases in the United
States show that pregnant women account for a
disproportionate number of deaths, making them a high-
priority group for vaccination (see
http://www.thelancet.com/journals/lancet/article/PIIS0140-6736(09)61304-0/abstract).
Also, guidance has been issued for clinicians to promptly
treat pregnant women who become infected with the 2009 H1N1
virus with antiviral drugs
(see http://www.cdc.gov/h1n1flu/clinician_pregnant.htm).
Q: Why aren't adults age 65 years and older included as a
priority group for the 2009 H1N1 vaccination as they are for
seasonal influenza, where they are included as part of the
age-50-and-older priority group?
A: Current studies indicate that the risk of infection,
hospitalization, and death from the 2009 H1N1 influenza
virus among persons age 65 years and older is less than is
the risk for younger age groups. Studies suggest that there
is some degree of preexisting immunity to the 2009 H1N1
strains, especially among adults older than age 60 years.
One possible explanation is that some adults in this age
group have had previous exposure, either through infection
or vaccination, to an influenza A (H1N1) virus. People age
65 years and older are included as a priority group if they
live with or care for infants younger than age 6 months or
are a healthcare or emergency services provider.
Q: Will H1N1 influenza vaccine be available for healthy
people age 25 years and older (who are not in targeted
groups)?
A: Once public health authorities at the local level
determine that the H1N1 influenza vaccine demand for the 5
target groups has been met, providers will be notified that
they can administer the vaccine to healthy people ages 25
through 64 years. Once demand for H1N1 influenza vaccine
among younger age groups is met, vaccination should be
expanded to all people age 65 and older.
Q: Once H1N1 influenza vaccine becomes available, should doctors
stop administering seasonal influenza vaccine?
A: No. Providers should start administering seasonal
influenza vaccine as soon as it is available and continue to
administer it throughout influenza season, including during
the winter and spring months.
Q: If a patient has received the seasonal influenza vaccine,
do they need to receive the H1N1 influenza vaccine?
A: If a patient is in a risk group to receive H1N1 influenza
vaccine, they should be vaccinated. Studies suggest that
vaccination with season influenza vaccine will not provide
protection against the 2009 H1N1 influenza virus.
Q: Will there be a new Vaccine Information Statement (VIS)
for the 2009 H1N1 influenza vaccine?
A: A new VIS will be developed that pertains only to the
2009 H1N1 vaccine. You will find it posted at
http://www.immunize.org/vis when it is available.
Q: In anticipation of H1N1 monovalent vaccine arriving later
this fall, CDC recommends that we begin vaccinating with
seasonal influenza vaccine now. Does protection from
seasonal influenza vaccine decline or wane within 3 or 4
months of vaccination? Should I wait until October or
November to vaccinate my elderly or medically frail
patients?
A: CDC recommends that seasonal influenza vaccine be
administered to all age groups as soon as it becomes
available. Antibody to seasonal inactivated influenza
vaccine declines in the months following vaccination.
However, antibody level at a point several months after
vaccination does not necessarily correlate with clinical
vaccine effectiveness. There are no studies that compare
vaccine effectiveness according to the month when the
vaccination was given. The authors of a recent review on
antibody declines among the elderly after vaccination
reported, "In conclusion, we found no compelling evidence
for more rapid decline of the influenza vaccine-induced
antibody response in the elderly, compared with young
adults, or evidence that seroprotection is lost at 4 months
if it has been initially achieved after immunization." (see
Skowronski et al., Rapid Decline of Influenza Vaccine-
Induced Antibody in the Elderly: Is It Real, or Is It
Relevant? Journal of Infectious Diseases 2008;197:490-502).
In addition, there is a lack of evidence for late season
outbreaks among vaccinated persons that can be attributed to
waning immunity.
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