An early estimate of flu vaccine efficacy showed it was only about 62 percent effective, the Centers for Disease Control and Prevention reported Friday. That is about average for seasonal flu vaccines, other studies show.
While the number of states reporting widespread flu, where more than 50 percent of local areas, such as counties, are seeing flu, rose from 41 to 47 in the latest reporting period, the CDC reported in its weekly FluView. However, the number of states experiencing high levels of flu activity declined from 29 to 24 and the overall percentage of patients who showed up with flu-like symptoms declined to 4.3 percent from 6 percent, CDC noted. The declines appear to be in the South and Southeast, where flu activity showed up this season first, but it is too early to say whether those areas are past their peak, said Dr. Thomas Frieden, the director of the CDC.
“Only time will tell us how long our season will last and how moderate or how severe this season will be in the end,” he said.
The season did have an unusually early start, about a month earlier than expected, Frieden said.
Medical College of Georgia, Doctors and University hospitals reported heavier caseloads of flu in November and December, but less recently.
“It hit hard and fast early on,” said Dr. Mark Newton, the medical director of the Emergency Room at Doctors Hospital. “Now it has slowed down a little bit here.”
Rates of people coming in with flu at University were much higher at the end of November and the beginning of December, said Dr. Craig Smith, the hospital’s medical director for infectious diseases. Where about half the people coming into the ER back then had flu-like illness, it was down to about 25-30 percent now, he said.
In fact, in a spotcheck of MCG’s and University’s Emergency Rooms Friday afternoon, there was not a single person there reporting flu-like symptoms.
Still, Frieden said, there is time for people to be vaccinated against flu if they have not already been. But in a CDC study of 1,155 people from Dec. 3 to Jan. 2, this year’s flu vaccine was 62 percent effective overall, showing about 55 percent efficacy against the more prevalent influenza A strain and 70 percent effectiveness against influenza B.
Historically, flu vaccines have ranged from about 50-70 percent effective in any given season, said Dr. Joseph Bresee, the chief of the epidemiology and prevention branch of the Influenza Division at CDC.
An analysis of flu vaccine effectiveness published last year in the journal Lancet Infectious Diseases found an overall efficacy of about 59 percent for seasonal flu vaccines studied over 12 seasons. A study published last year from the Australian National Centre for Epidemiology and Population Health of seasonal flu vaccine effectiveness from 2007 to 2011 found overall effectiveness was 62 percent, with results ranging from 31 percent against the seasonal influenza A H1N1 strain to 88 percent effectiveness against the pandemic A H1N1 strain.
“What we’ve know for a long time is the flu vaccine is far from perfect, but it is still by far the best tool we have to prevent the flu,” Frieden said.
Even if the person still gets the flu, getting the vaccine can result in a milder illness that could make a big difference in vulnerable populations, Smith said.
“Especially in elderly people and people with bad chronic diseases (such as diabetes), while they may still get sick, the vaccine effect decreases mortality,” he said.