Can you still get the flu even if you have been vaccinated?

 

 

Posted by Donna Lazorik, RN, MS. Donna is the Immunization Coordinator in the Division of Epidemiology and Immunization at the Massachusetts Department of Public Health.

Over the past few weeks, DPH has received a lot of questions concerning how well this year’s vaccine matches the kinds (or “strains”) of flu that are currently circulating, and why it might be that vaccinated people can still get the flu.  

Every year, some people who are vaccinated against influenza still get sick and test positive for flu.  It’s not possible at this time to say whether or not there is more of this happening this season than usual.  What we do know is that this is an early season, with more influenza activity being reported at this time than has been seen during recent flu seasons.  DPH and the U.S. Centers for Disease Control and Prevention (CDC) are watching the situation closely and will provide additional information as it becomes available. 

There are, however, a number of reasons why people who got a flu vaccine may still get sick this season:

1. People may be exposed to an influenza virus shortly before getting vaccinated or during the two-week period that it takes the body to gain protection after getting vaccinated.  This exposure may result in a person getting the flu before the vaccine begins to protect them.

2. A person may be exposed to an influenza virus that is not included in the seasonal flu vaccine.  There are many different influenza viruses that circulate every year.  The composition of the flu shot is reviewed each season and, if necessary, updated to protect against the 3 viruses that research suggests will be most common. Studies of the flu viruses collected this season indicate that most circulating viruses are like the vaccine viruses (a good match).  However, there is a smaller percentage of viruses that would not be expected to be covered by the vaccine.  

Each year, DPH sends a small sample of flu specimens tested at the State Laboratory to the CDC so they can identify the flu viruses and determine whether they are consistent with what is included in this season’s vaccine.  So far this season, CDC has tested three specimens from Massachusetts and all three were viruses included in the vaccine.  Nationally, 91% of the samples tested by CDC have been consistent with viruses included in the vaccine.

3. Unfortunately, some people can get infected with an influenza virus that is included in the vaccine even if they have been vaccinated.  Protection provided by flu vaccination can vary widely, based in part on the health and age of the person getting vaccinated.  In general, the flu vaccine works best among young healthy adults and older children, although it does not provide 100% protection even among these groups.  Some older people and people with certain chronic illnesses may develop less immunity after vaccination.  However, even in people that do not respond as well to the vaccine, the flu vaccine still provides some level of protection, and may result in less severe illness if they become sick with the flu.

All that being said, vaccination is still the best tool currently available to prevent the flu. If you have not already been vaccinated, it still makes sense to get the flu vaccine.  In Massachusetts, flu season usually peaks in February, and continues through April and May.  Contact your healthcare provider to schedule an appointment, or go to www.mylocalclinic.com to find a clinic near you.

For more information about the flu, visit www.mass.gov/flu. 

Comments

[Rich]

Me and my wife got the flu this week after we got vaccinated in October. I read about the strains but it looks like there are done that were missed or unaccounted for. Not all cases are submitted for testing.

[Bethany botts]

I currently have the flu and I did not get my kids vaccinated. I am so worried that they will get this. I have quarantined myself to my bed room and sent my children to their grandparents house the past two days. Should they still get a flu shot? Or should I take them to their dr and ask them to be started on tarmi flu suspension?

DPH RESPONDS: It is never too late to get a flu shot, so by all means please consider getting one for your children (over six months) and yourself. The decision to take Tamiflu to prevent influenza after an exposure is best discussed with your pediatrician.

[Ken Johnston]

Hi,

In late October, early November I received an Influenza Virus vaccine (Fluzone) by Sandfi-Pasteur for H1N1; H3N2; B/Texas/6/11 from my local Western Mass. doctor. Do I need to get another?

DPH RESPONDS: If you are an adult and you received a dose of Fluzone in the fall of 2012, you do not need to get another – until next flu season. Two doses would only be recommended for some children under the age of nine.

[Judy Aurin]

Both myself and my daughter got the flu over Christmas and New Years, My daughter started Christmas seven days later on New years even I came down with it. I Missed a week of work, with Cough, Cold, Fever Chills, Body Aches and Lethargy I slept for four days. It been 10 days for me now.. feeling better still have a horrific cough and sound like my head is in a can when I speak... and guess what! we both had a flu shot In late October 2012!!!!!!!!!!!!!! So what's the deal.

DPH RESPONDS: A lot of folkshave been asking about this so we thought it would be helpful to walk through why some people may still get sick after being vaccinated. Check out our latest blog post and let us know if you have any more questions! http://publichealth.blog.state.ma.us/2013/01/can-you-still-get-the-flu-even-if-you-have-been-vaccinated.html

[Jennifer Brown]

Hi Donna,

Great information, thanks for communicating. Can the flu vaccine prevent or lessen complications related to other strains of the flu virus?

Thanks,
Jennifer

DPH RESPONDS: Thanks for your question. Yes, the influenza vaccine can provide some protection (called cross-protection) against different but related strains of flu viruses.

According to the CDC, the ability of flu vaccine to protect a person depends on two things: 1) the age and health status of the person getting vaccinated, and 2) the similarity or “match” between the virus strains in the vaccine and those circulating in the community. If the viruses in the vaccine and the influenza viruses circulating in the community are closely matched, vaccine effectiveness is higher. If they are not closely matched, vaccine effectiveness can be reduced.

However, it’s important to remember that even when the viruses are not closely matched, the vaccine can still protect many people and prevent flu-related complications. Such protection is possible because antibodies made in response to the vaccine can provide cross-protection against different, but related strains of influenza viruses.