The recent increase in serious disease caused by varicella and resulting complications, in both children and adults, have made its prevention desirable. Varicella vaccine, which was licensed in March 1995, is recommended by the Advisory Committee on Immunization Practices and the American Academy of Pediatrics. Although administering multiple vaccines at a single visit is convenient, lower varicella antibody response has been seen when varicella vaccine was combined with measles-mumps-rubella (MMR) vaccine and administered in a single vaccine as MMRV. Shinefield and colleagues studied the immunogenicity and safety of varicella vaccine administered concurrently at a separate site with MMR and a combination diphtheria, tetanus toxoids and pertussis (DTP)– Haemophilus influenzae type b vaccine (DTP-Hib conjugate combination, or DTP/HbOC) as opposed to single administration of varicella vaccine six weeks after concomitant administration of MMR and DTP/HbOC.

A total of 609 infants were randomly assigned to one of two groups: one receiving MMR, DTP/HbOC and varicella vaccines at the same time but at separate injection sites, and the second receiving varicella vaccine six weeks after the concomitant administration of MMR and DTP/HbOC vaccines. All participants were followed clinically for local or systemic reactions to injection. Serologic immunities were measured approximately one year after vaccination.

Significantly more pain and soreness occurred when varicella vaccine was given concomitantly than when it was given six weeks after the other two vaccines. Irritability and temperature of at least 38.°C (102°F) was significantly more frequent following concomitant administration of the three vaccines. At one-year follow-up, mean titers were similar in both groups for all viral antigens. Six cases (three from each group) of varicella occurred within 42 days of vaccination. Two cases (both from the first group) of varicella were reported after 42 days of vaccination.

The authors conclude that since the antibody responses and the number and severity of varicella cases occurring within 42 days of vaccination were similar following both courses of immunization, the administration of varicella vaccine, MMR and DTP/HbOC at the same visit but at separate injection sites is as effective as varicella vaccine administration at a separate visit.

editor's note: Administration of varicella vaccine has been hindered by both physicians' and parents' concerns about efficacy, length of immunity and side effects, and a perception that chicken pox is a benign disease. Studies in the United States show good humoral and cellular immunity up to 10 years after vaccination, while experience in Japan shows maintenance of active immunity by vaccination for 20 years in over 90 percent of initial responders. Safety has been documented, with the most common adverse effect being a brief, localized reaction to the injection. A few cases of mild symptoms with a varicella-like rash have been reported. Physicians need to more strongly advocate for vaccination of susceptible children and adults, since chicken pox is not always benign, especially if contracted after childhood. The World Health Organization has noted that universal administration of this varicella vaccine may not be a high priority for developing nations where cost considerations are more important.—r.s.