H1N1 Vaccine Boosts Immune Response in Asthmatics

A single dose of H1N1 vaccine is safe and induces a strong immune response predictive of protection, according to a clinical trial of inactivated H1N1 flu vaccine in people with asthma.

The findings also suggest that individuals over the age of 60 who have severe asthma may require a larger dose of vaccine.

“Asthma was the most common underlying health condition among those hospitalized in the United States with 2009 H1N1 influenza infection during the 2009-2010 influenza season,” says NIAID Director Anthony S. Fauci, M.D. “The results of this clinical trial show that the 2009 H1N1 influenza vaccine was safe and led to adequate production of antibodies thought to be protective against the virus. This is important because the H1N1 vaccine is one component of the seasonal influenza vaccine currently being distributed for the 2010-2011 influenza season.” [Read more…]

Study Models H1N1 Flu Spread

As the United States prepares for the upcoming flu season, a group of researchers continues to model how H1N1 may spread.

The work is part of an effort  called the Models of Infectious Disease Agent Study (MIDAS), to develop computational models for conducting virtual experiments of how emerging pathogens could spread with and without interventions. The study, supported by the National Institutes of Health, involves more than 50 scientists with expertise in epidemiology, infectious diseases, computational biology, statistics, social sciences, physics, computer sciences and informatics.

As soon as the first cases of H1N1 infections were reported in April 2009, MIDAS researchers began gathering data on viral spread and affected populations. This information enabled them to model the potential outcomes of different interventions, including vaccination, treatment with antiviral medications and school closures. The work built upon earlier models the MIDAS scientists developed in response to concerns about a different potentially pandemic influenza strain H5N1 or avian flu.

“Computational modeling can be a powerful tool for understanding how a disease outbreak is unfolding and predicting the implications of specific public health measures,” said Jeremy M. Berg, Ph.D., director of the National Institute of General Medical Sciences, which supports MIDAS. “During the H1N1 pandemic, MIDAS scientists applied their models to see what they could do to help in a real situation.”

Because the H1N1 flu strain is still circulating, a MIDAS group based at the University of Washington in Seattle is now studying the impact the virus could have this fall and winter. Its model, which represents the world population, includes information about immunity — how many people are protected by vaccination or prior infection—and the other circulating flu strains. Using the model, the scientists may be able to predict how H1N1 evolves and the possible role of the H3N2 strain, which historically has been the dominant seasonal flu virus. The results also may help forecast the potential effectiveness of the new flu vaccine that includes both the H1N1 and H3N2 viral strains.

Estimating Severity

To predict the likely severity of H1N1 in the fall and winter months following the initial outbreaks, the MIDAS group led by Marc Lipsitch, D.Phil., of the Harvard School of Public Health in Boston analyzed patient care data from Milwaukee and New York City. The researchers estimated that about 1 in 70 symptomatic people were admitted to the hospital, 1 in 400 required intensive care and 1 in 2,000 died. They predicted H1N1 to be no more and possibly even less severe than the typical seasonal flu strain. The work, which factored in local differences in flu detection and reporting, also showed that it’s possible to make predictions about severity using data from the early stages of an outbreak.

Vaccinating Children

Ira Longini, Ph.D., at the University of Washington and his MIDAS colleagues developed a simulation model to evaluate the effectiveness of different strategies to vaccinate school-aged children, who are known to play a key role in transmitting the flu virus. They modeled a range of scenarios that varied the type of vaccine, the percentage of children vaccinated and the infectiousness of the virus. For each situation, the modeling results indicated that vaccinating this age group substantially reduced overall disease spread and prevented up to 100 million additional cases in the general population. These effects, however, were less strong when the virus was more contagious or when fewer children were vaccinated. Based on these results, Longini’s group concluded that vaccine distribution strategies should depend on a number of factors, including vaccine availability and viral transmission rates.

Cost-Benefit of Employee Vaccination Programs

In one of the first analyses of the economic value of work-sponsored seasonal and pandemic flu vaccine programs, the MIDAS group led by Donald Burke, M.D., at the University of Pittsburgh developed a model that estimated the employer cost to be less than $35 per vaccinated employee with a potential savings of $15 to $1,494 per employee, depending on the infectiousness of the virus.

Interventions and Local Demographics

To determine if a vaccination strategy would likely have the same effect in different locations, a team led by MIDAS investigator Stephen Eubank, Ph.D., of the Virginia Bioinformatics Institute at Virginia Tech in Blacksburg developed models representing the demographics of Miami, Seattle and each county in Washington. The models indicated that while vaccinating school-aged children was the best strategy in each place, the optimal timing and overall effectiveness of the approach varied due to specific characteristics of the local population, such as age, income, household size and social network patterns. These differences, Eubank concluded, suggest that vaccination and probably other intervention strategies should take local demographics into account.

Antiviral Medications

Lipsitch’s collaborators Joseph Wu, Ph.D., and Steven Riley, D.Phil., at the University of Hong Kong used mathematical modeling to predict the likelihood that the H1N1 strain would develop resistance to the widespread use of antiviral medications taken to lessen flu symptoms. Their work showed that giving a secondary antiviral flu drug either prior to or in combination with a primary antiviral could mitigate the emergence of resistant strains in addition to slowing the spread of infection. The results, the researchers concluded, point to the value of stockpiling more than one type of antiviral drug.

School Closures

A public health measure under consideration was closing schools, which previous MIDAS pandemic flu models identified as a potentially effective intervention. According to Burke’s model of Allegheny County, Penn., closing individual schools after they identified cases may work as well as closing entire school systems. When strictly maintained for at least 8 weeks, both types of school closure could delay the epidemic peak by up to 1 week, allowing additional time to develop and implement other interventions. However, the model also indicated that school closures lasting less than 2 weeks could actually facilitate flu spread by returning susceptible students to school in the middle of an outbreak.

“Models like the ones MIDAS has developed help us understand not only trends in disease spread, but also how different factors can influence those trends,” said Irene A. Eckstrand, Ph.D., who directs the MIDAS program. “MIDAS research is leading to new tools and approaches that can aid in making public health decisions at a range of levels, from local to national.”

Source: National Institutes of Health (NIH), September 21, 2010

World Health Organization Declares End to H1N1 Influenza Pandemic

The World Health Organization (WHO) International Health Regulations (IHR) Emergency Committee and the WHO Director-General, Dr. Margaret Chan, today declared an end to the 2009 H1N1 influenza pandemic. This declaration was based on strong indications that influenza, worldwide, is transitioning toward seasonal patterns of transmission.

In the majority of countries, out-of-season 2009 H1N1 outbreaks are no longer being observed, and the intensity of 2009 H1N1 influenza virus transmission is lower than that reported during 2009 and early 2010. Members of the Emergency Committee further noted that the 2009 H1N1 viruses will likely continue to circulate for some years to come, taking on the behavior of a seasonal influenza virus.

This does not mean that the H1N1 virus has disappeared. Rather, it means current influenza outbreaks including those primarily caused by the 2009 H1N1 virus, show an intensity similar to that seen during seasonal epidemics. Pandemics, like the viruses that cause them, are unpredictable. WHO noted that continued vigilance is extremely important, and it is likely that the virus will continue to cause serious disease in younger age groups and pregnant women, at least in the immediate post-pandemic period.

The WHO Director-General ended the Public Health Emergency of International Concern in accordance with the International Health Regulations (2005).

Implications for United States
This is a formal WHO declaration regarding the end of the pandemic at the global level. The U.S. Public Health Emergency determination for 2009 H1N1 Influenza expired on June 23, 2010.

The only impact on the United States resulting from the WHO declaration will be a cessation in weekly reporting under the International Health Regulations (IHR) to the Pan American Health Organization and the World Health Organization. CDC has reported weekly to IHR since early in the pandemic.

There are no changes for the United States in terms of CDC’s recommendations for the upcoming influenza season and the United States is already proceeding with the understanding that the 2009 H1N1 virus is now part of seasonal influenza virus circulation.

Protecting Yourself and Others from Influenza
CDC recommends a three-step approach to fighting flu: vaccination, everyday preventive actions and the correct use of antiviral drugs if your doctor recommends them. The first and most important step in protecting against the flu is to get a flu vaccine each season.

The U.S. 2010-2011 influenza vaccine will protect against an H3N2 virus, an influenza B virus, and the 2009 H1N1 influenza virus that caused the first global pandemic in more than 40 years and resulted in substantial illness, hospitalizations and deaths. In the United States, the CDC’s Advisory Committee on Immunization Practices recently recommended that everyone 6 months of age and older be vaccinated against influenza each season. Pregnant women, young children, and anyone with underlying health conditions like asthma, diabetes and neuromuscular diseases are at especially high risk for influenza-related complications and, therefore, should be vaccinated as soon as vaccine becomes available. Vaccine manufacturers are predicting an ample supply of influenza vaccine for the upcoming 2010-2011 U.S. influenza season.

Source: CDC, August 10, 2010

Pregnant Women Should Take Greater Care of Novel H1N1 (“Swine Flu”) Virus

A recent study indicates that pregnant women are more severely impacted by a new H1N1 flu virus and should seek immediate treatment with antivirals.

Pregnant women infected with 2009 novel H1N1 had a higher rate of hospitalization and greater risk of death than the general population due to the H1N1 flu.

The data collected and analyzed by the Centers for Disease Control and Prevention (CDC) are the most comprehensive available to date on the impact of this novel H1N1 flu virus among pregnant women.

“The death of a pregnant woman is always heartbreaking, and unfortunately we have been hearing reports of otherwise healthy women dying from H1N1. If a pregnant woman feels like she may have influenza, she needs to call her healthcare provider right away,” said CDC′s Dr. Denise Jamieson, lead author of the study. “Clinicians who treat pregnant women should have a system in place for triaging pregnant women with influenza-like symptoms and they should not delay in initiating appropriate antiviral therapy. Some clinicians hesitate treating pregnant women with antiviral medications because of concerns for the developing fetus, but this is the wrong approach. It is critical that pregnant women, in particular, be treated promptly. ”

Six deaths of pregnant women with H1N1 were reported to CDC between April 15 and June 16, 2009, representing 13 percent of the total 45 deaths reported to CDC during that time period. All were healthy prior to infection of H1N1 and subsequently developed primary viral pneumonia leading to acute respiratory distress requiring mechanical ventilation. All pregnant women who died did not receive antivirals soon enough to benefit their treatment. CDC recommends that pregnant women with suspected or confirmed influenza infection receive prompt treatment with antiviral medication.

Based on past influenza pandemics and on seasonal influenza epidemics, pregnant women have increased rates of illness and death from influenza infection.

Despite recommendations from the Advisory Committee on Immunization Practices and the American College of Obstetricians and Gynecologists for inactivated flu vaccine for all pregnant women, seasonal flu vaccine coverage among pregnant women is very low (less than 14 percent).

Source: Centers for Disease Control (CDC), July 29, 2009; Lancet, August 8, 2009.