Health and Science News for Parents
Feb
21

Flu is really bad this year – and the vaccine’s been pretty good

written by Tara Haelle

You’ve probably already been hearing what a bad season it is for the flu. The news is awash with tragic stories of otherwise healthy children and even adults without underlying conditions succumbing to this year’s influenza. Because I am pregnant, the ones that hit me the hardest are the stories of pregnant women – especially those who did not get the flu shot – losing their babies and even their own lives to the flu. But the most tragic irony is that this season, those suffering and dying the most are the very folks who often skip out on the flu shot… because they’re healthy adults. In fact, early season estimates by the CDC put the flu vaccination rate at 39.5% for all ages. usmap7

When I wrote about top myths about the flu vaccine in October, some commenters took issue with the need for healthy young adults to get the flu shot, especially if they were not going to be around children or the elderly (and therefore feel a responsibility to prevent transmission). Among the inaccurate myths I countered were that the flu isn’t that bad and that people don’t die from the flu if they’re healthy. Unfortunately, this year’s flu season is a textbook case for why they’re horribly wrong.

The most recent CDC FluView summary, ending February 15, reports over 7,000 laboratory-confirmed influenza cases in the U.S. (The actual numbers of flu this year are far higher since many who have the flu never get the laboratory-confirmed flu test, and the rapid test has a high false-negative rate, especially during times when flu prevalence is high in the population.) The most frequently circulating strain this season is the influenza A H1N1 virus, one which was included in this year’s vaccines and which tends to hit young and middle-aged adults particularly hard.

As this week’s CDC Morbidity and Mortality Weekly Report shows, the concern for healthy adults has borne out, and the single biggest factor shared among those becoming severely ill or dying from the flu are that they did not get their flu shot this year. (And it’s not too late! You can still get one!) In fact, adults aged 18 to 65 account for nearly two thirds (61%) of all hospitalizations for the flu this year. Ironically, this year’s season is not as bad as last season in terms of total cases, but you’re hearing so much about flu because so many healthy adults are dying from it this year.

Another somewhat sad irony is that the flu shot is particularly effective this year given that it included the H1N1 strain. The MMWR also reported on the mid-season estimates of the vaccine’s effectiveness, based on data from 2,319 children and adults who had acute respiratory illness and were enrolled in the U.S. Influenza Vaccine Effectiveness Network from December 2013 through January 2014. Researchers look at all these cases and then assess how many had received the flu vaccine and how many had not.

Based on these calculations, the flu vaccine was 61% effective this year in preventing people of all ages from needing to go to the doctor or hospital due to the flu. (Because there is no way to track those who don’t go to a doctor or hospital, researchers can only track effectiveness of the shot in terms of those more serious cases. This means the findings may underestimate the effectiveness of the vaccine.) Against the H1N1 strain in particular, the vaccine was 62% effective across all age groups for the same protection.

Together, these findings add support to the research letter published February 10 in the American Journal of Respiratory and Critical Care Medicine. That letter outlined preliminary findings regarding those requiring treatment in the ICU for the flu this year. Among the patients included in that study, the median age for hospitalization for the flu was 28.5 years old. That means half the patients were younger than 28 and half were older (ranging from 2 months old to 101 years old).

Although the study was small, involving only 55 patients, the researchers found that 87% were sick with the H1N1 strain, and only 24% had been vaccinated at least two weeks before becoming ill. (As I’ve noted previously, the vaccine is never 100% effective, and it is unfortunately possible to get the flu despite getting the vaccine. But as we just saw above, the vaccine does considerably reduce a person’s risk of illness – and therefore increase likelihood of survival.) Forty percent of those patients were then admitted to the ICU, and three of the overall 55 patients died. (At the time of the letter, 18 were still hospitalized.)

One interesting finding in this letter is that 32% of those admitted to the ICU (7 of the 22 patients) had previously been tested for the flu and received a negative result, including four rapid tests. This finding underscores the fact that this year’s flu estimates are well below the actual incidence since the false negative rates for lab-confirmed tests are substantial.

So, the bottom line is pretty clear: This year’s flu season is especially bad if you’re a “young, healthy adult.” This year’s flu vaccine is particularly effective in preventing the very strain that is hitting young adults hard. And it’s not too late to get a flu shot.

For more data, charts and graphs about this year’s flu season, check out the CDC’s FluView. For a helpful Q&A about this year’s flu, check out this Mother Jones piece from January.

4 Responses to “Flu is really bad this year – and the vaccine’s been pretty good”

  1. Lisa Bailey

    Thanks for this info. I noticed that the “healthy children” link in the first paragraph goes to an article on circumcision. I would be really interested to see the intended article.

  2. Pennie

    I think you mean “false negatives” at the end of your penultimate paragraph, otherwise CDC numbers would be overestimates, and the power of your argument falls apart…

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