The two-year shortage of two childhood vaccines--one for diphtheria, tetanus and whooping cough and the other for measles, mumps and rubella--is over, the Centers for Disease Control and Prevention in Atlanta announced Thursday.
Doctors can resume scheduled booster vaccinations for toddlers and preschoolers that were postponed to conserve supplies. Infants, considered most vulnerable, had continued to receive their initial shots, but not follow-up inoculations.
"We're relieved we have vaccine in time for the start of school," said Dr. Natalie Smith, immunization branch chair for the California department of health services. Smith is with the Advisory Committee on Immunization Practice, which made the conservation recommendations to the CDC's National Immunization Program in 2001.
No outbreaks were reported nationally as a result of the shortages, health officials said.
Renewed supplies of the vaccines still are being shipped to doctors and hospitals so some will not be fully stocked for several weeks, said Curtis Allen, the CDC program's spokesman.
"It was an empty pipeline so there's a distribution lag," he said. Parents should call physicians to verify that enough vaccine is available.
A number of factors contributed to the shortage of vaccines. The only U.S. manufacturer of MMR, Merck & Co., temporarily stopped production to upgrade its facilities, the CDC said.
A shortage of the tetanus component of the DTaP vaccine limited production. Also, one major manufacturer of DTaP suddenly dropped out of the market, said John Modlin, chairman of the CDC advisory panel.
But two months ago, the Food and Drug Administration approved a new vaccine, Daptacel, from another manufacturer, which eased the shortfall.
Regulatory changes affected supply as well. In 1999 the CDC and the American Academy of Pediatrics recommended removing a mercury-based preservative from all vaccines, which caused several companies to stop production.
It can take a year from start to finish to make a batch of vaccine, said Sara Radcliffe, a research director for the Pharmaceutical Research and Manufacturers of America, which represents drug companies.
There is not a lot of incentive for companies to make older vaccines, Modlin said. As a result, during the last 40 years, fewer manufacturers have produced them, Radcliffe said.
Two other vaccines still are in limited supply, Allen said. Shortages of chicken pox vaccine should be alleviated by the end of July or the beginning of August. And the recently approved pneumococcal conjugate vaccine, which prevents childhood pneumonia and meningitis, may not be ready until year's end, the CDC spokesman said.
Wyeth Lambert, the only manufacturer of the pneumococcal vaccine, has not met its demand since it was approved in October, Modlin said.
Some organizations recommend that the CDC stockpile routine childhood vaccines to guard against shortages.
"The situation with MMR would have been much, much worse, but there were some stockpiles," said Ann Margaret Arvin, professor of pediatrics and microbiology at Stanford University and a member of the CDC's National Vaccine Advisory Committee.
But maintaining adequate supplies--and getting them to kids--is key to preventing disease. "It doesn't take many susceptible children to have an outbreak," Arvin said.
Children typically receive five diphtheria, or DTaP, vaccinations: at 2, 4 and 6 months with booster shots scheduled for 15 to 18 months and again between 4 to 6 years. During the shortage, doctors held off on the last two shots.
Infants usually receive their first MMR shots at 12 to 15 months. Without adequate supplies, however, physicians were asked to postpone the second shot, typically administered from the ages of 4 to 6.