Seasonal pneumococcal carriage rates varied in day care centers

Pneumococcal carriage shows high seasonal variation, especially in day care centers, according to recent study findings published in The Pediatric Infectious Disease Journal.

Jonas Ahl, MD, PhD, of the infectious diseases unit in the department of clinical sciences at Skane University Hospital in Sweden, and colleagues examined day care center personnel and children aged 0 to 7 years (49% female; median age, 44 months) at 109 Swedish day care centers for 10 years.

Of the screened children, 42% were pneumococcal carriers and younger children were more likely carriers.

In the second year of life pneumococcal carriage rates were 57% followed by 53% in the third year, 44% in the fourth, 34% in the fifth, 30% in the sixth and 27% in the seventh.

There was a dip in carriage rates in July and August with smaller dips in January and April.

“We noted a significant lower carriage rate after major holidays and leaves,” the researchers wrote. “Even though January is a month with a high incidence of viral infections, there was a dip in carriage rate. We believe that the seasonal variation is mainly due to absence from the [day care center] environment.”

Overall, 1,305 day care personnel were cultured and 4.5% (95% CI, 3.7-6.2) were positive for pneumococci.

“In summary, this study is made from a unique and large material of nasopharyngeal cultures from [day care center] personnel and children from a period of more than 10 years,” the researchers wrote. “[Day care center] group size has not been proven to be a risk factor for pneumococcal carriage. To the best of our knowledge, group size has not been proven to be a risk factor for pneumococcal carriage, even though this has been believed in theoretical grounds. We also suggest that the seasonal variation in pneumococcal carriage is due to absence from the [day care center]. These findings support the thesis that crowding in the [day care center] should be avoided if dispersion of pneumococci should be restricted. Carriage rate in personnel was found to be higher compared to a normal population.”

Disclosure: The study was funded in part by Skane County Council's Research and Development Foundation.One researcher reports being a member of Pfizer’s Swedish pneumococcal advisory board.