As China prepares to institute a new influenza vaccination program, findings by Chinese and American scientists suggest that a staggered program is necessary for three different climate regions across the country.

A study conducted by researchers from the Chinese Center for Disease Control and Prevention (China CDC) and members of the National Institutes of Health Fogarty International Center (NIH) on data from 88 cities over seven years found that flu activity in northern China spikes during the winter, while southern China experiences a peak in the summer. The mid-region of China, which includes Shanghai, experiences spikes in February and May.

As a result, the one-size-fits-all vaccination programs utilized by most countries would be less effective in China, according to Cecile Viboud, a researcher at NIH and co-author of the report. China should instead schedule vaccination shipments beginning in October for northern regions, and February for southern regions. The mid-region of China should anticipate two spikes, and plan accordingly.

The country currently does not have a national vaccination program, although a vaccine is available for purchase privately and through local government programs in Beijing and a few other cities.

"The climatic differences require very different immunization strategies," Viboud told China Daily. "Many countries assume that because they are in the northern or southern hemisphere, they can go by the standard suggestions for other countries, but this is not true in China."

No other country utilizes a staggered vaccination program, but the findings of the report are similar to those found in Brazil, which also encompasses several different climate zones.

Around 2 percent of people in China receive a flu shot each year, while around 30 percent of Americans receive one, the study found. Government estimates put the annual death rate from flu at around 11-to-18 per 100,000 people in China, with death rates in rural areas about two to three times higher than those in urban areas, Viboud said.

Although climate accounts for the disparity between Chinese regions, population mobility can also impact the way in which flu epidemics develop, Viboud said. She noted that Hong Kong and Shenzhen — neighboring cities in southern China — experienced notably different rates of flu incidence before travel restrictions were lifted between the two cities, indicating that the movement of people can impact flu rates more than climate alone.

The collaboration between NIH and China CDC researchers suggests that the Chinese government will factor the findings of the report into a new nationwide flu vaccination program, expected to be implemented in the coming years, Viboud said. More broadly, the study might also be useful in underscoring the importance of localized health data.

"As routine immunization campaigns are rolled out and local vaccine production improves in resource-limited regions, it will become increasingly important to ensure that vaccination strategies are optimally tailored to the local epidemiology of the disease," the report said.

Contact the writer at Kdawson@chinadailyusa.com