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Vaccination, antiviral therapy safe, effective for pregnant women
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During the 2009 influenza A (H1N1) pandemic, debate arose over whether vaccines and antiviral treatments would be safe for use in pregnant women, but recently published data indicate these vaccines and treatments are not only safe but are essential in preventing illness during this vulnerable period, according to a speaker in Atlanta at the 2010 International Conference on Emerging Infectious Diseases.
Richard Beigi, MD, MSc, of the Magee-Women’s Hospital of the University of Pittsburgh said that pregnant women are more prone to various infections for several reasons, ranging from immunological changes to alterations in the dynamics of lung function resulting from fluctuating progesterone levels. Little data exist, however, on therapeutic interventions in this population, he said.
To understand the effect that H1N1 has on pregnant women, analyzing previous influenza pandemics is important, said Beigi. He cited two studies, one conducted during the 1918 Spanish flu pandemic and another from the Asian flu circulating in the 1950s, that showed 50% higher mortality rates for pregnant women when compared with the general population. Additionally, one study revealed a spike in mortality rates among pregnant women aged 15 to 34 years — an especially relevant finding as it mirrors the population most affected during the recent pandemic, he said.
Data accrued during the 2009 H1N1 pandemic were deceptive, according to Beigi. The median age of those with the disease was 20 years, which is unusual for seasonal influenza, and the overall case fatality rate was less than 1%, which was similar to seasonal influenza. Many cases also resolved without treatment. However, this disease course was not the same for pregnant women.
Although the mortality rate among the entire population was low from the pandemic strain, the number of deaths among pregnant women was disproportionately high, he said. The data from the current H1N1 influenza pandemic were consistent, however, with data from previous influenza pandemics.
Promising vaccines
The H1N1 vaccine showed the most promise as a preventive measure, according to Beigi. The seasonal influenza vaccine is currently recommended through all three trimesters, and past studies have demonstrated its safety in pregnant women. Furthermore, a recent study indicated the vaccine is 62% effective in preventing disease while also staving off respiratory illness and fever. Therefore, physicians should continue to administer the H1N1 vaccine to pregnant women.
Previous analyses also reveal that maternal vaccination is one of the most cost-effective interventional strategies that can be performed in medicine. This is also partly due to the neonatal protection afforded by immunizing the pregnant mother. Immunization rates among this population, however, have yet to reach 50%.
Another recent study examined the timing of treatment with disease onset, said Beigi. Fifty-six of 800 pregnant women died during the research period. Only one death, however, occurred among those treated within 1 to 2 days of symptom onset; therefore, the importance of early treatment has now been re-emphasized among pregnant women as well as other special populations.
Beigi acknowledged that studies regarding appropriate doses of anti-influenza medications in pregnant women are ongoing, but he said previous research investigating the use of standard doses of oseltamivir (Tamiflu, Roche) in 61 pregnant women raised no red flags. Similarly, zanamivir (Relenza, GlaxoSmithKline) lacks any biological evidence for harm in this population and the package insert also note the drug works best within 24 hours of symptom onset.
Rapid access to antiviral medications and ensuring that pregnant women not only recognize the signs and symptoms of influenza but understand the importance of early intervention are required for appropriate treatment in this population, said Beigi. – by Melissa Foster
Beigi R. N3. Presented at: 2010 International Conference on Emerging Infectious Diseases; July 11-14, 2010; Atlanta.