One-third of family physicians did not defer booster doses during a national shortage of Haemophilus influenzae type b, or Hib, vaccine, despite an interim recommendation to that effect made by the CDC in consultation with its Advisory Committee on Immunization Practices, or ACIP; the AAFP; and the American Academy of Pediatrics, or AAP.
A study(pediatrics.aappublications.org) in the May issue of Pediatrics found that 98 percent of pediatricians and 81 percent of family physicians surveyed were aware of the interim recommendations during the shortage, but 22 percent of pediatricians and 33 percent of family physicians reported not deferring the booster.
Researchers said that physicians in both specialties were less likely to adhere to recommendations if they thought their practices had adequate supplies of Hib vaccine.
Merck & Co. Inc. recalled about 1 million doses of its Hib vaccines -- PedvaxHIB and the combination Hib/hepatitis B vaccine COMVAX -- in December 2007 after routine testing of equipment used to manufacture the vaccines identified the presence of the pathogen Bacillus cereus.
In response to the recall and resulting vaccine shortage, the CDC, the AAFP and the AAP recommended temporarily deferring the Hib booster in healthy children not at high risk for invasive Hib disease. CDC officials further urged clinicians to track children in whom the booster was deferred so they could be recalled for immunization when the supply problem improved.
Merck subsequently suspended production of the two Hib-containing vaccines, and the interim recommendations stayed in place for more than 18 months.
The CDC, the Academy and the AAP reinstated the booster dose in June 2009 after vaccine manufacturer Sanofi Pasteur helped fill the Hib vaccine gap with increased distribution of its monovalent Hib vaccine, ActHIB, and its combined diphtheria, tetanus toxoids, acellular pertussis, inactivated poliovirus and Hib, or DTaP-IPV/Hib, vaccine, which is marketed as Pentacel.
In August 2009, GlaxoSmithKline's monovalent Hib vaccine, Hiberix, was approved by the FDA for booster doses in children ages 15 months to 4 years, further alleviating the shortage. Soon thereafter, the CDC recommended that physicians recall children who had not received a Hib booster dose.
Merck's PedvaxHib returned to the market in January 2010, but COMVAX remains unavailable. (Editor's Note: COMVAX returned to the market in August 2010.)
According to the Pediatrics study, during the prolonged shortage, 73 percent of pediatricians and 45 percent of family physicians who treat children reported insufficient Hib vaccine supplies, and more than 20 percent of physicians in both specialties reported having to defer doses in the primary series for infants 2-6 months old.
In addition, 21 percent of pediatricians and 37 percent of family physicians surveyed said they thought the interim recommendations were unclear. However, the study's researchers hypothesized that the lack of clarity actually had less to do with the recommendations themselves than it did with the varying formulations of the Merck and Sanofi vaccines and the fact that the competing products required different numbers of doses to complete their respective primary series.
Regardless, the authors contended that the difficulties such vaccine shortages impose on primary care practices, coupled with the potential for losing ground in the battle against once-prevalent vaccine-preventable diseases, "point to the need for national policy efforts to stabilize vaccine supplies."