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Childhood Vaccines Have Prevented 100 Million Infections in U.S.: Study

26 million infections averted in past decade alone, says study

WEDNESDAY, Nov. 27, 2013 (HealthDay News) -- Childhood vaccinations have prevented more than 100 million infections in the United States since 1924, a new database reveals.

In just the past decade, more than 26 million infections have been averted, researchers report.

Funded by the U.S. National Institutes of Health and the Bill & Melinda Gates Foundation, the database tracks reportable diseases back to 1888. Scientists say it helps them better understand how contagious diseases such as measles, polio and chicken pox spread. They can also determine what preventive measures have been most effective.

"The dramatic declines of incidence rates around the time of vaccine licensures was much more striking than we anticipated," said Dr. Willem van Panhuis, an assistant professor of epidemiology at the University of Pittsburgh Graduate School of Public Health. Van Panhuis used the database for the new study on vaccine effectiveness.

"One of the motivations for doing this work is the resurgence of some vaccine-preventable illnesses, like measles and whooping cough. Using this database, we can see when these epidemics occur," noted van Panhuis.

Results of the study and details about the new publicly available database are in the Nov. 28 issue of the New England Journal of Medicine.

In 2012, more than 38,000 cases of whooping cough were reported in the United States -- the most since 1959, according to background information in the study. And, even though a vaccine for measles has been available in the United States since 1963, outbreaks of measles still occur.

These worrisome disease revivals may be due to parents refusing to get their children vaccinated, the researchers said.

Because immunization programs have become so successful, most people with young children today have never lived with the threat of potentially deadly infectious diseases such as smallpox or polio. They may underestimate the threat of such diseases as a result.

And some may falsely assume if others are vaccinated, that will help protect their children by keeping the incidence of these diseases low. However, recent whooping cough and measles outbreaks have occurred in children who were intentionally under vaccinated.

Some parents choose not to have their children vaccinated because of a now-debunked and retracted study published in 1998 that suggested that the measles, mumps and rubella (MMR) vaccine might cause autism. It was later reported that the study's author, Dr. Andrew Wakefield, had doctored some of the study's results.

Since that initial study came out, multiple researchers have looked at the issue. The most recent study that failed to find an association between multiple vaccine exposure and the development of autism was published in the August issue of the Journal of Pediatrics.

The developers of the new database hope that this information can be used to provide clear evidence of the benefits of vaccines to those who are skeptical.

The database includes weekly surveillance reports of 56 nationally notifiable infectious diseases for U.S. cities and states from 1888 through 2011. Almost 88 million individual cases are included.

To estimate how many infections were prevented after the introduction of a vaccine, the researchers used the data from the historical incidence of the disease and projected that it would have continued to spread at the same rate if the vaccine hadn't become available.

"Our study provides good estimates of what the impact of vaccination has been and what the dangers of a lack of immunization are," said van Panhuis.

Dr. Kenneth Bromberg, director of the Vaccine Research Center at the Brooklyn Hospital Center, said this information is interesting but still preliminary. "The database can't yet answer a lot of detailed questions," he said.

However, he said it's important to have access to this type of reporting. "A lack of knowledge of what it was like before vaccines shouldn't be an excuse to let our guard down," Bromberg said.

"Look at what's going on with polio," he added, referring to the recent discovery of the polio virus in Israel's sewage system. Polio was one of the most feared diseases of the 20th century, crippling around 35,000 people each year in the United States in the late 1940s and early 1950s, according to the U.S> Centers for Disease Control and Prevention. Because of vigorous vaccination, the United States became polio- free in 1979.

In Israel, Bromberg said, "they're worried that infections could start up again. We have to remember that these things aren't far away."

More information

Learn more about the childhood diseases that can be prevented with vaccines from the U.S. Centers for Disease Control and Prevention.

SOURCES: Willem van Panhuis, M.D., Ph.D., assistant professor, epidemiology, University of Pittsburgh Graduate School of Public Health, Penn.; Kenneth Bromberg, M.D., director, Vaccine Research Center, Brooklyn Hospital Center, New York City; Nov. 28, 2013, New England Journal of Medicine
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