ERUSALEM, Aug. 21 — The Israeli security cabinet decided today to vaccinate 15,000 security, medical and rescue personnel against smallpox because of the possibility that Iraq might respond to any American attack with a biological strike on Israel.

The Health Ministry was already vaccinating about 1,500 public health workers, but a vaccination of the entire population was not planned unless the threat became real.

No government has produced any evidence that Iraq has the smallpox virus, which was declared eradicated by the World Health Organization in 1980. No one, however, has been able to rule out the possibility that it obtained some from Russia.