Kids’ Vaccine Makes Elders Healthier

Give children a pneumococcal vaccine, and their parents and grandparents may be healthier, according to researchers here.

The widespread use of the pneumococcal conjugate vaccine (PCV-7) for children under the age of five has caused a dramatic decline in invasive pneumococcal disease among those 50 and older, according to Catherine Lexau, Ph.D., of the Minnesota Department of Health.

“We think it’s really a type of herd immunity,” Dr. Lexau said. Young children are the most frequent carriers of pneumococcal bacteria, she said, so immunizing them creates a “ripple effect” that benefits their elders.

Strikingly, among those 65 and older, the decline in pneumococcal disease was so great that it has already exceeded the 2010 goal set by the CDC, Dr. Lexau and colleagues reported in the Oct. 26 issue of the Journal of the American Medical Association.

With colleagues, Dr. Lexau studied invasive pneumococcal disease in nearly 19 million people older than 50 in eight states, using data collected by the CDC’s Emerging Infections Program at locations including her health department.

The CDC data covered the two-year period before the pediatric vaccine was licensed in 2000 and the four years immediately afterward.

The study found:

* The rate of invasive pneumococcal disease fell 28% among adults aged 50 and older, with a 95% confidence interval ranging from 24% to 31%.
* The rate in 1998-1999—the first year studied—was 40.8 cases per 100,000 people. At the end of the study, in 2002-2003, it was 29.4.
* For those over 65, the 2002-2003 rate—41.7 cases per 100,000—was lower than the CDC’s 2010 goal of 42 cases per 100,000.

The pediatric vaccine contains the seven pneumococcal serotypes considered most likely to cause disease in children, but omits 16 others that are included in the 23-valent polysaccharide adult vaccine.

Dr. Lexau and colleagues found the decline in disease caused by those seven serotypes was especially dramatic—55%, with a 95% confidence interval ranging from 51% to 58%.

At the same time, disease caused by the other 16 serotypes did not decrease, they found. Disease caused by serotypes not found in either vaccine showed a slight increase over the study period, from 6.0 to 6.8 cases per 100,000 people.

The PCV-7 vaccine has caused a “very amazing decline” in invasive pneumococcal disease among children under five, said Jon Temte, M.D., Ph.D., a professor at the University of Wisconsin and a liaison to the advisory committee on immunization practices for the American Academy of Family Physicians.

Indeed, for the seven serotypes included in the vaccine, the reduction was 94% (with a 95% confidence interval ranging from 92% to 96%), according to the CDC’s Sept. 16 Morbidity and Mortality Weekly Report.

The added benefit for older Americans demonstrated by Dr. Lexau’s study, Dr. Temte said, is “icing on the cake, as it were.”

“This is an indication that by reducing the disease burden and carriage of the most common causes of invasive pneumococcal disease among children, we are also having a large impact on other people,” he said.

While the study is not nationwide, Dr. Lexau said, the researchers are confident it reflects a real phenomenon. In the study areas, the investigators obtained data from every reference lab and hospital and periodically checked records to ensure that no cases had been omitted.

“We are trying to capture every single case of these serious pneumococcal infections that occur in the population,” he said.

Also, the size of the study population gives them confidence that the findings can be generalized, she said. “Our population isn’t identical to the U.S. population, but we have a big enough population base that we can project (the findings) to the U.S. population,” she said.

Dr. Lexau said the study has several take-home messages for clinicians. One is that the PCV-7 vaccine is having a major beneficial effect outside its target population.

But the second message is that they shouldn’t neglect adult vaccinations, she said, because disease caused by other serotypes showed no decrease and in some cases rose slightly.

Finally, she said, physicians should make a special effort to vaccinate adults with co-morbid conditions, such as diabetes or HIV, because they appeared to get little no benefit from the indirect effect of the PCV-7 vaccine.

In fact, the proportion of cases of pneumococcal disease rose significantly among some groups of patients with co-morbid conditions after the introduction of the pediatric vaccine.

The number of cases reported to be HIV-positive in 1998-1999, for instance, was 1.7% of the 2,955 people with a comorbid condition. In 2002-2003, it was 5.6% of 2,390.

“We think physicians should be more vigilant about vaccinating those high-risk groups with the adult pneumococcal vaccine,” she said.

Primary source: Journal of the American Medical Society

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