CDC: Smallpox responders wouldn't need revaccination in outbreak

Sep 25, 2003 (CIDRAP News) – Centers for Disease Control and Prevention (CDC) officials say healthcare workers who recently received smallpox shots would not need a second shot in the event of a smallpox outbreak in the next few years, despite a recent CDC advisory suggesting that they might.

A CDC guideline on smallpox vaccination and procedures, updated Aug 18, states that all smallpox team members should "maintain an up-to-date vaccination status. The appropriate interval for revaccination of [smallpox] response team members is currently under review and will be made available in the near future. In addition, upon confirmation of a smallpox outbreak, a repeat vaccination to boost the immune system response may be indicated for all team members to ensure their greatest protection."

But CDC spokesman Von Roebuck said people who were successfully vaccinated in the current program would not need another shot in the event of an outbreak. "In no way are we saying that if you were vaccinated already, you need to be vaccinated again," he told CIDRAP News.

The issue surfaced this week in San Diego. County health officials there took the CDC guideline to mean that they should revaccinate the local smallpox response team members if the disease re-emerged, according to a report in the San Diego Union-Tribune.

Roebuck said the intent of the guideline is to say that vaccinees eventually may need to be revaccinated. "That would be down the road, 5 to 7 to 10 years," when their immunity "perhaps could wear off," he said.

The duration of immunity resulting from a smallpox shot varies, but the consensus of smallpox authorities such as Dr. D. A. Henderson is that it usually begins to wane after 5 to 10 years.

Roebuck stressed that recent vaccinees who had a "take"—the characteristic lesion signaling an immune response—would be protected from smallpox if they had to respond to an outbreak anytime soon. "If they had a take, they're good to go," he said.

"We've said nothing in the sense that people who have been vaccinated in the past year of the program need to be revaccinated now," Roebuck said.

See also:

CDC document "Smallpox Vaccination Status and Procedures—Guidelines for Grantees using Licensed Undiluted Wyeth Dryvax Vaccine"

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