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Hib vaccine coincides with sharp decline in periorbital and orbital cellulitis
Study finds all cases of orbital cellulitis associated with sinusitis.
BOSTON — The introduction of the Haemophilus influenzae B (Hib) vaccine has coincided with a sharp decline in the number of periorbital and orbital cellulitis cases related to H. influenzae, according to a retrospective, comparative case series involving 315 pediatric inpatients at two Massachusetts hospitals.
“We expected that H. influenzae would be decreased, but we didn’t expect to see such a decrease in the overall caseload of orbital and periorbital cellulitis,” said Balamurali K. Ambati, MD, a senior resident in ophthalmology at the Massachusetts Eye and Ear Infirmary here. These two conditions “decreased by a much greater percentage than you would expect by simply eliminating H. influenzae.”
The first Hib vaccine was introduced in 1985 and was licensed initially for children between the ages of 2 and 5. A second vaccine followed in 1990 for use in children 2 months of age or older. That same year, Massachusetts mandated Hib vaccination in children.
Cutoff year
The discharge databases of the two hospitals yielded 342 cases of periorbital and orbital cellulitis between January 1980 and August 1998. However, 27 of these cases were excluded, primarily because of incomplete medical records and, to a lesser extent, underlying immunodeficiency. Of the remaining 315 cases, 11 patients were admitted twice (each case was considered separately).
A total of 297 cases of periorbital cellulitis and 18 cases of orbital cellulitis were recorded. The mean age of children with periorbital cellulitis was 3.2 years versus 5 years for orbital cellulitis. There were no significant differences in age between the two patient groups before and after 1990. The year 1990 was selected as the cutoff date because, as previously noted, this was the same year Massachusetts mandated Hib vaccination.
Upper respiratory infection was associated with 73 cases of periorbital cellulitis and 10 cases of orbital cellulitis, while sinusitis was associated with 44 cases of periorbital and 18 cases of orbital. Otitis media was also associated with 32 cases of periorbital and three cases of orbital. “All 18 cases of orbital cellulitis had associated sinusitis,” Dr. Ambati told Ocular Surgery News about the recently published study in Ophthalmology. “This is an important message to the clinician when trying to distinguish between periorbital and orbital cellulitis. I believe the presence of sinusitis probably merits a more thorough workup.”
Unexpected decline
Among the 230 cases of both forms of cellulitis occurring before 1990, 27 (11.7%) had proven Hib infection, compared with only three of 85 cases (3.5%) after 1990 (P=0.028). But, 76 cases (33.0%) before 1990 developed culture-positive isolates versus nine (10.6%) after 1990 (P<0.001). Furthermore, since 1992, only one case of Hib-related cellulitis has occurred, which was in a child who had recently emigrated from Haiti.
The authors noted that the Centers for Disease Control reports a 99% decrease of Hib invasive disease from 1989 through 1995. “Recent studies have also indicated a definite decline in Hib-related orbital and periorbital cellulitis,” Dr. Ambati said. Although the present study supports these findings, it also poses an intriguing question: “Why have the entities of periorbital and orbital cellulitis themselves declined, along with positive culture isolates, out of proportion to the elimination of Hib-related disease?” the authors stated.
“A complete elimination of Hib would be expected to reduce total incidence of periorbital and orbital cellulitis by approximately 35%,” Dr. Ambati said, referring to the 30 of 85 cases with positive cultures that grew Hib. However, “the annual incidence fell from 21.2 before 1990 to 8.7 afterward, which is a reduction of 59%.”
The authors propose “that perhaps Hib was not only an active pathogen, but also facilitated the pathogenesis of other organisms.” The authors are hopeful that this hypothesis will stimulate future investigation. “The presence of copathogens may be unrelated to the cellulitis,” Dr. Ambati said. Moreover, “the use of oral antibiotics before admission may have suppressed growth of Hib in some of our cases.”
Confounding factors
Because the decline in the number of cellulitis cases admitted over the past decade is not easily attributed to Hib vaccination alone, the authors offer many possible confounding factors. These include a higher threshold for hospital admission, improved general child health and earlier and more aggressive use of antibiotics for outpatient patients. The cyclic nature of H. influenzae may also play a role. For example, the rate of infection was relatively low in the early 1980s, followed by a rapid rise later in the decade. The severe winters in the Boston area in the mid-1980s paralleled with a great increase in Hib cases. Finally, the “herd immunity” effect from Hib vaccination may magnify the reduction of Hib infections over time.
Still, “I think skin flora and pneumococcus are probably the two main agents we need to worry about, so antibiotic coverage should be changed accordingly,” Dr. Ambati said. On the other hand, Dr. Ambati is impressed with the high Hib vaccination rate in Massachusetts. “The latest report indicated that 95% of children in the Boston area are up-to-date with their vaccination coverage,” he said. “This contrasts with other states” that do not have nearly the compliance rate.
For Your Information:References:
- Balamurali K. Ambati, MD, can be reached at the Department of Ophthalmology, Massachusetts Eye and Ear Infirmary, 243 Charles St., Boston, MA 02114; (617) 523-3844, pager ID 2050; fax: (617) 573-3365; e-mail: bambati@yahoo.com.
- Ambati BK, Ambati J, Azar N, et al. Periorbital and orbital cellulitis before and after the advent of Haemophilus influenzae type B vaccination. Ophthalmology. 2000;107:1450-1453.