By Liz Highleyman

Typical seasonal influenza mainly poses a risk for very young and elderly people and others with weak immune systems. The H1N1 flu, however, has caused an unusually high proportion of severe illness and death among older children and young adults (most of whom have had other underlying health conditions), and in particular pregnant women.

As of July 24, 2009, CDC had received reports of 43,771 laboratory-confirmed H1N1 cases, 5011 hospitalizations, and 302 deaths in the U.S.

ACIP held a meeting in July to discuss the spread of H1N1 and to determine vaccination prioritization and implementation. When the H1N1 vaccine -- now undergoing intensive development -- first becomes available, ACIP recommends that programs and providers make it a priority to vaccinate the following groups:

	Pregnant women.
	People who live with or care for children younger than 6 months of age.
	Health care and emergency services personnel.
	Persons between the ages of 6 months and 24 years.
	People between the ages of 25 and 64 years who are at higher risk due to chronic health disorders or compromised immune systems.

The advisory panel indicated that the key populations include people who are at higher risk of disease or complications, those who are likely to come in contact with novel H1N1, and those who could infect young infants. However, the agency's epidemiology figures indicate that the highest proportion of deaths -- 41% -- have occurred in people aged 25-49, followed by 24% in the 50-64 age group, neither of which are included in the priority list unless they have other health conditions. Only 2% of deaths so far have occurred in children age 4 or younger.

Altogether, the 5 highest priority groups comprise nearly 160 million people, which exceeds the projected initial vaccine supply. ACIP also released a narrower list -- comprising about 40 million people -- to be used if the vaccine has limited availability. This list includes pregnant women, household contacts of infants younger than 6 months, a subset of health care workers and emergency personnel who have direct patient contact, children aged 6 months through 4 years, and children aged 5 to 18 years who have underlying risk factors that put them at risk for flu complications.

ACIP recommended that health care providers continue to emphasize the importance of regular seasonal influenza vaccination and ensure that patients receive these vaccines as soon as they become available -- particularly people aged 65 and older, who are not on the H1N1 vaccine priority list.

"The H1N1 outbreak so far has spared that population to a large extent," said Anne Shuchat of the CDC's National Center for Immunization and Respiratory Diseases. "After younger age groups have been addressed, if supply is adequate vaccination could be offered at that time."

For more information from the meeting and the resulting recommendations, visit the ACIP meeting website.

Pregnant Women

While the absolute number of pregnant women severely affected by H1N1 to date has been small, the percentage is high considering the proportion of pregnant women in the population at any given time.

As reported in the August 8, 2009 issue of The Lancet, 6 of the 45 H1N1-associated deaths reported to the CDC between April and June -- or 13% -- occurred among otherwise healthy pregnant women. Furthermore, pregnant women who contract H1N1 flu are at least 4 times more likely to be hospitalized.

Pregnant women suspected of having H1N1 should receive oseltamivir (Tamiflu) as soon as possible, even before completion of diagnostic testing, according to the study authors.

"Testing is not available in many instances and, when available, results of novel H1N1 testing often takes several days," according to the CDC's interim guidance for pregnant women. "Clinicians should be aware of circulation of H1N1 in their area and not wait for test results to initiate influenza treatment in women who have symptoms consistent with influenza illness."

"Some clinicians hesitate to treat pregnant women with antiviral medications because of concerns for the developing fetus, but this is the wrong approach," said lead author Denise Jamieson of CDC's U.S. Public Health Office. "It is critical that pregnant women in particular be treated promptly."

Global Epidemic

In related news, the World Health Organization (WHO) in late July issued a report estimating that the novel H1N1 flu could infect as many as 2 billion people -- or about 1 in 3 worldwide -- over the next 2 years. The virus has now spread to all regions and almost every country, according to the agency.

To address the crisis globally -- and ensure that limited vaccine and flu drug supplies do not all go to high-income countries -- United Nations Secretary-General Ban Ki-Moon urged wealthy nations to help developing countries access the H1N1 vaccine so that health workers can be vaccinated and able to keep hospitals open.

During a recent Mercosur South American trade summit, presidents Cristina Kirchner of Argentina and Luiz Inacio Lula da Silva of Brazil proposed that developing countries be allowed to suspend patent rights so they can produce more H1N1 vaccine than licensed manufacturers can manage. Using patent rights to preserve an economic advantage, said Kirchner, "would condemn millions of people to death."

Pharmaceutical company Baxter International announced on August 8 that it has completed production of its first commercial batches of H1N1 vaccine. The same day, Novartis announced that it has launched the first human trials of its candidate vaccine.The year-long trial will involve 6000 people in the U.S., U.K., and Germany.

While efforts to develop, test, and produce an effective H1N1 vaccine have been put on the fast track, the WHO emphasized that this would not compromise safety or quality control.

8/18/09

Sources

ACPM Headlines. CDC Advisory Panel Recommends H1N1 Vaccine Priority List. Press Release. August 6, 2009.

Kaiser Family Foundation. H1N1 Could Infect Up To 2B People Within Next Two Years, WHO Says. Kaiser Daily Global Health Policy Report. July 27, 2009.

Kaiser Family Foundation. Fast-Tracked H1N1 Vaccines Will Not Compromise Safety, WHO Says. Kaiser Daily Global Health Policy Report. August 6, 2009.

Reference

DJ Jamieson, MA Honein, SA Rasmussen, and others. H1N1 2009 influenza virus infection during pregnancy in the USA. The Lancet 374(9688): 451-458. August 8, 2009. (Abstract).