Flu cases in Massachusetts are rising rapidly, especially among kids in Boston, where hospitalizations of children under five have increased 150% over the last two weeks.

With the state reporting the deaths of four children from the flu, including two under the age of two in Boston, health officials are now sounding alarms.

"We have not had a pediatric flu death in Boston since 2013, so that fact, and given the fact that we have seen some really sick kids and severity of illness is a concern," Boston Public Health Commissioner Dr. Bisola Ojikutu said. 

Cases "heading straight up"

Tufts Medicine Chief Infection Control Officer Dr. Shira Doron explained how this bad flu season is mirroring last year's bad flu season, but this time, it started one month earlier.

"A year ago, we were saying, whoa, things are headed straight up but we were already in January, and so here, things are heading straight up but this was still December," Dr. Doron said. "It could be a long-drawn-out season, or it could be a short season. One never knows."

Doron says the virus has mutated, making it not well matched with the current flu vaccine. She said the amount of cases are "threatening things like availability of hospital beds."

But pediatrician Dr. Robyn Riseberg, who is often the first stop for kids suffering from the flu, says vaccination is still the best line of defense to prevent severe disease. She says she is telling patients to get their flu shots, "as soon as they can." 

Only about 30% of Boston residents are vaccinated against the flu. Starting on Wednesday, the Boston Public Health Commission is setting up six flu vaccine clinics. The clinics are free, and no insurance is required.