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Flu Season 2018-2019: How Are We Doing So Far?

March 14, 2019

The high-severity of the 2017-2018 flu season has put flu vaccinations at the top of the priority list for many people. Early season flu vaccination coverage reports show that flu vaccination rates have increased compared to the same time last year. 45.6 percent of children ages 6 months to 17 years have received a flu vaccination, which is an increase of 6.8 percent compared to last year, and 44.9 percent adults received a flu vaccination – an increase of 6.4 percent compared to last year.

The efficacy of the seasonal influenza vaccine can vary each season depending on how well matched the vaccines are to the circulating strains. While influenza vaccinations are generally between 40 and 60 percent effective in any given year, vaccination is still the best defense against the flu and prevents a substantial number of influenza-related illnesses, hospitalizations and deaths annually. During last year’s brutal flu season, when the flu shot had relatively low effectiveness compared to other years, it is estimated that vaccination prevented 7.1 million illnesses, 3.7 million medical visits, 109,000 hospitalizations and 8,000 deaths during the 2017-2018 season.

According to the mid-season report from the Centers for Disease Control and Prevention (CDC), the vaccine for the 2018-19 flu season has been 47 percent effective overall and 61 percent effective for children ages 6 months through 17 years. Explaining some of the differences between the 2017-2018 and the 2018-2019 seasons, CDC spokeswoman Kristen Nordlund said that the main strain of influenza A circulating this year is H1N1, a strain which “the vaccine tends to perform better against.” And that last year, another strain, H3N2, was more predominant, which could have contributed to the severity of the season because even though the vaccine protects against H3N2, it is not as effective against the virus. The 2017-2018 vaccine effectiveness was about 40 percent across all age groups for influenza A and B and estimated to have been only 24 percent effective against the H3N2 strain for all age groups.

The CDC estimated that this year’s flu season has sickened between 17.7 million and 20.4 million nationwide. This includes an estimated 13,600 to 22,300 deaths, according to public health estimates. While these numbers may seem high, the CDC stated in the mid-season report that this year’s flu season has been a low-severity influenza season, with a lower percentage of outpatient visits for influenza-like illness, lower rates of hospitalization and fewer deaths attributed to pneumonia and influenza, compared with recent seasons.

So far, the 2018-2019 vaccine is a good match to the influenza viruses that are circulating, which has increased the effectiveness. With increased effectiveness and increased vaccination rates, we may see an overall more mild season, but it is not over yet. Influenza activity remains elevated in the United States, and the season may not have peaked. Influenza B has not made much of an appearance and that strain tends to show up closer to spring, which highlights the importance of continued vaccination, given that flu season can continue well into April. Anyone over 6 months of age who has not yet been vaccinated this season is encouraged to get vaccinated as soon as possible.

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