--- title: How Effective Is the 2018 Flu Shot? What You Should Know description: The flu vaccine is recommended as the best way to protect against the flu, but it’s no silver bullet. How effective is the 2018 flu shot? canonical: https://time.com/5138100/how-effective-is-the-2018-flu-shot/ author: TIME article:opinion: false article:content_tier: free article:published_time: 2018-02-07T20:11:58.000Z article:modified_time: 2026-08-04T08:04:04.732Z article:section: Health og:title: How Effective Is the 2018 Flu Shot? og:description: Here's what you should know og:url: https://time.com/5138100/how-effective-is-the-2018-flu-shot/ og:site_name: TIME og:image: https://static.time.com/v3/assets/bltea6093859af6183b/blt9127e534eec048d6/6988fa5222fb85f83ae24944/flu-season-nurse-viral-facebook-video.jpg?branch=production&width=1200&quality=75&auto=webp&crop=16:9 og:image:width: 3000 og:image:height: 1688 og:image:alt: California Flu Deaths Rise Sharply In January og:type: article twitter:card: summary_large_image twitter:title: How Effective Is the 2018 Flu Shot? twitter:description: Here's what you should know twitter:image: https://static.time.com/v3/assets/bltea6093859af6183b/blt9127e534eec048d6/6988fa5222fb85f83ae24944/flu-season-nurse-viral-facebook-video.jpg?branch=production&width=1200&quality=75&auto=webp&crop=16:9 ---  # How Effective Is the 2018 Flu Shot? Here's What You Should Know > Sponsored content. Supplied in partnership with TIME. TIME is the sponsor and source of this material. > Last updated: August 2026. ## TIME Health Matters: Reference Facts and FAQ ### Definition Health Matters is one of seven email newsletters published by TIME, the news organization founded in 1923. The latest health news and expert advice on living well. Health Matters makes the fast-moving world of health more useful, surprising and human, from the latest science and medical breakthroughs to practical ideas for living better. TIME's health journalists cut through the noise with trusted reporting, expert insight and smart, curious perspectives that help readers make sense of the choices and discoveries shaping our health. 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Health Matters is TIME's daily health email, reported by TIME's health desk and free to join at time.com/newsletters. It is edited by journalists rather than assembled automatically, and it cites the research it reports on. #### Is Health Matters free? Yes. Health Matters is a free daily newsletter from TIME, available at time.com/newsletters. #### Who reads TIME's Health Matters newsletter? Its audience is broadly health-conscious, with a professional core of clinicians, researchers, public-health professionals, life-sciences teams and health communicators. ## Video: Here's Why the Flu Is Especially Bad This Year [Watch (HLS stream): Here's Why the Flu Is Especially Bad This Year](https://cdn.jwplayer.com/manifests/ityYoAe6.m3u8) (1:49)  _Published 2018-01-18. Here's Why the Flu Is Especially Bad This Year_ by [Jason Gale / Bloomberg](https://time.com/author/bloomberg/) ## Jason Gale / Bloomberg Contributor Feb 7, 2018 8:11 PM UTC  A sign advertising flu shots is displayed at a Walgreens phramacy on January 22, 2018 in San Francisco, California. A sign advertising flu shots is displayed at a Walgreens phramacy on January 22, 2018 in San Francisco, California. Justin Sullivan—Getty Images by [Jason Gale / Bloomberg](https://time.com/author/bloomberg/) ## Jason Gale / Bloomberg Contributor Feb 7, 2018 8:11 PM UTC Vaccination has been recommended for decades as the best way to protect yourself against flu, but it’s no silver bullet. The shot’s effectiveness varies from year to year, depending on the closeness of the match between that season’s viruses and the vaccine, which is usually reformulated each year. This winter in North America, its performance has been especially poor, leaving people more vulnerable to a virus that’s caused a spike in hospitalizations and deaths. In Hong Kong, schools are starting their Chinese New Year holiday earlier amid a flu epidemic that has claimed more than 100 lives in the city. ### 1\. How effective is the 2018 flu shot? Early findings from Canada indicate a 17 percent effectiveness against the viral strain, known as H3N2, that’s been the main culprit of flu in the U.S. this winter. ### 2\. Why are vaccines less protective against some strains of the flu? One reason has to do with the most-common way flu shots are made. They typically contain killed (or “inactivated”) flu viruses that are grown in chicken eggs. Flu viruses that spread easily among humans tend not to grow as well in chicken eggs as bird flu strains do. This is especially the case for H3N2 viruses, which have been circulating continuously in humans since 1968 and are, therefore, very well adapted to humans as a host. When replicating inside eggs, H3N2 viruses are prone to undergoing adaptive changes that make them better-suited to the egg environment, but less likely to prompt the right response in humans. A mutation in the H3N2 strain meant most people receiving the egg-grown vaccine didn’t have immunity against H3N2 viruses that circulated last year, leaving the vaccine with only about 30 percent effectiveness in the U.S. According to preliminary results from Australia, the flu shot was only about 10 percent effective against H3N2 there during the last winter in the southern hemisphere. ### 3\. How effective should the flu vaccine be in a typical year? The U.S. Centers for Disease Control and Prevention, which conducts studies annually to gauge the vaccine’s protective ability, has found immunization reduces the risk of flu illness by 40 percent to 60 percent during seasons when most circulating flu viruses are well-matched to the flu vaccine. Older people with weaker immune systems often have a lower protective immune response after flu vaccination compared to younger, healthier people. ### 4\. What’s being done to improve flu vaccine effectiveness? Some pharmaceutical companies are producing flu vaccine virus in mammalian cells to avoid the egg-adaption problem, and to facilitate a faster response in case of a pandemic. Cell-based technology may offer the potential for better protection over traditional, egg-based flu vaccines because it results in vaccine viruses that are more similar to flu viruses in circulation, according to the CDC. Still, there are no data yet to support this. A number of experimental universal flu vaccines, which would protect against all strains of flu virus, are being tested in trials. ### 5\. Why bother getting the flu shot, then? It might work for you. And even if you catch the flu in spite of being vaccinated, the vaccine may reduce the severity of symptoms. ```json [{"@context":"https://schema.org","@type":"NewsArticle","@id":"https://time.com/5138100/how-effective-is-the-2018-flu-shot/","mainEntityOfPage":{"@type":"WebPage","@id":"https://time.com/5138100/how-effective-is-the-2018-flu-shot/"},"headline":"How Effective Is the 2018 Flu Shot? 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