H1N1 VACCINATION GUIDELINESS

July 30, 2009 (Atlanta, Georgia) — New H1N1 influenza vaccine recommendations from the Centers for Disease Control and Prevention (CDC) suggest priority distribution among 5 groups.

The CDC announced the recommendations in a press conference held after an "urgent" meeting of the Advisory Committee of Immunization Practices yesterday.

Recommended Target Groups

Anne Schuchat, MD, director of the National Center for Immunization and Respiratory Diseases with the CDC, announced that the Advisory Committee of Immunization Practices recommends that 5 target groups receive the vaccine:

• Pregnant women,
• household contacts of children who are younger than 6 months of age,
• healthcare workers and emergency medical services personnel,
• children and young people between the ages of 6 months and 24 years of age, and
• nonelderly adults with underlying risk conditions or medical conditions that increase their risk for complications from influenza.

The committee also addressed the issue of what to do in the event of a vaccine shortage and how to prioritize those groups who should receive the vaccine.

"In general, under most circumstances, we really ought to promote vaccine in all of these 5 focus groups, and...picking them or prioritizing some before others would not benefit the public," Dr. Schuchat said. The CDC's estimate of the target groups totals 159 million individuals, but "there's a lot of overlap in some of the groups...[it is] probably a lower number than that," she said.

"Just in Case" Prioritization Group

However, the Advisory Committee of Immunization Practices also proposed a priority group consisting of a much smaller group, about 41 million individuals, that should be vaccinated in the event of a shortage. These include

• Pregnant women,
• household contacts of children who are younger than 6 months of age,
• healthcare workers and emergency services personnel who have direct patient contact or direct contact with infectious substances,
• children between the ages of 6 months and 4 years of age, and
• children 5 to18 years of age who have underlying risk factors that put them at greater risk for complications of influenza.

According to Dr. Schuchat, the real operating assumption is that they will "go forward with the broader group," she said.

Seasonal Influenza Vaccine Remains Important

According to the CDC, the seasonal influenza vaccine remains very important. "Our assumption is that it is very likely [that seasonal influenza and H1N1 vaccines] can be given together," Dr. Schuchat told Medscape Infectious Diseases during the briefing. "There will be more data coming out...but it is likely they can be given at the same visit," she said. According to Dr. Schuchat, 2 doses of the vaccine will probably be needed, with 15 μg antigen/dose.

"The recommendations make sense on the basis of what we know about this virus," said John Bartlett, MD, chief of the Johns Hopkins University School of Medicine, Division of Infectious Diseases, Baltimore, Maryland.

"Of interest is the observation that persons over 64 years, a high priority for seasonal flu vaccine, are not included here," he told Medscape Infectious Diseases. "That decision is based on the curious observation that the people born before 1957 appear to be relatively well protected from infection or serious disease with this strain of H1N1 virus." According to Dr. Bartlett, it appears that a similar strain circulated before 1957, accounting for this protection; other comparable viruses also have circulated more recently.

"Pregnant women and young people seem to be especially susceptible to [the H1N1] influenza strain and also to bad outcomes when infected," he said. "But the elderly should get [the] seasonal flu vaccine, since they account for the vast majority of the 36,000 deaths attributed to seasonal influenza in the average season" he added. "In fact, most people should get seasonal flu vaccine. The current indications for that vaccine apply to about 80% of the US population."

Production a Concern

Dr. Schuchat noted that the production of the H1N1 vaccine could be unpredictable. "Right now, we are to on track, expecting vaccine doses in the fall," she said, adding that "exactly how many [doses will be available] exactly when will be tough to pinpoint."

"Production is a concern, since the novel H1N1 virus does not grow well in eggs, and 2 doses are likely to be necessary," said Dr. Bartlett. If the virus thrives in the fall in the Northern hemisphere, "it will be a challenge to be ready," he said.