BURLINGTON — The number of whooping cough cases in Vermont has dropped in half since a vaccination and public information campaign was launched in December, the state Health Department said Tuesday.

Last year the state reported a record number of 645 cases of whooping cough, a number the state considered an epidemic.

On Dec. 19, the Health Department sponsored a special vaccination day to immunize people. Since then, hundreds more Vermonters have gotten shots.

Whooping cough is a highly infectious bacterial disease that is most serious for babies too young to be fully vaccinated. Its name comes from the sound children make as they gasp for breath.

Last year at this time 89 whooping cough cases had been reported in Vermont, while so far this year there have been 42.

“We can’t declare the end of this outbreak, but we’re thankful that Vermonters responded as they did to slow the spread of illness,” said Health Commissioner Dr. Harry Chen. “Cases spiked at the end of the year and have steadily decreased since then.”

Preliminary government figures showed in January that the country had suffered its worst year for whooping cough in nearly six decades.