Tag: HBsAg

Why Can’t You Give Blood After Getting a Vaccine?

If you are like most people, you have heard so much anti-vaccine misinformation that you figure it is safe to assume that everything these folks say isn’t true.

Yes, go research shedding

If you are a true skeptic, you will still do your research on any new claims just to make sure.

Why Can’t You Give Blood After Getting a Vaccine?

Although you may not have heard of any restrictions on donating blood after getting vaccinated before, it makes sense once you think of it.

You actually have to wait:

  • for up to 8 weeks after getting the smallpox vaccine
  • for up to 4 weeks after getting the MMR (because of the rubella component), chickenpox, and Zostavax vaccines.
  • for up to 3 weeks after getting the hepatitis B vaccine
  • for up to 2 weeks after getting the measles, mumps, oral polio, or yellow fever vaccines

If you notice that these are almost all live vaccines, it becomes very easy to see why you can’t donate blood shortly after being vaccinated.

Blood donation is “Acceptable if you were vaccinated for influenza, tetanus or meningitis, providing you are symptom-free and fever-free. Includes the Tdap vaccine. Acceptable if you received an HPV Vaccine (example, Gardasil).”

American Red Cross Eligibility Criteria: Alphabetical

Live vaccines can create a temporary viremia (virus particles in the blood), which could then be transferred to someone else in donated blood.

Could you get an infection this way?

Probably not.

Remember, you would only be getting the attenuated or weakened vaccine virus strain and even then, it would be a very small amount. If the person getting the vaccine doesn’t get sick from getting the vaccine, why would someone who was getting a much smaller dose through a blood donation.

Still, there is a theoretical risk, especially if the person who received the blood donation had an immunodeficiency, so people aren’t supposed to donate blood shortly after getting these vaccines.

But what about the hepatitis B vaccine. It isn’t a live virus vaccine.

The risk with this vaccine is that a very recently vaccinated donor might test positive for HBsAg (this only happens temporarily), leading the donation center to actually think that they had a hepatitis B infection, disqualifying them from ever donating blood again.

Does any of this mean that vaccines aren’t safe?

Of course not!

Just consider some of the other restrictions on donating blood:

  • You are not eligible to ever donate if you ever tested positive for hepatitis B, even if you were never sick.
  • You must wait 12 months after your last contact if you were exposed to someone with hepatitis B and you want to donate blood.
  • If you are unvaccinated, you must wait at least 4 weeks after being exposed to someone with measles.

So yes, that means that you will be much more likely to be eligible to donate blood if you are fully vaccinated and protected.

More on Donating Blood After Getting Vaccinated

How Often Should You Do Vaccine Titer Testing?

We sometimes hear about folks doing vaccine titer testing.

A vaccine titer is a blood test that can determine whether or not you are immune to a disease after you get a vaccine.

While that sounds good, after all, why not check and be sure, it has downsides. Chief among them is that the results aren’t always accurate.

That’s right. You can sometimes have a negative titer test, but still be immune because of memory B cells and the anamnestic response.

How Often Should You Do Vaccine Titer Testing?

So how often should you do vaccine titer testing?

It depends, but most folks might never have it done!

Why not?

Vaccines work very well, so you would typically not need to routinely check and confirm that you are immune after being vaccinated. And, this is also important, the vaccine titer tests don’t always work that well, titer testing isn’t available for all vaccines (you can’t do titer testing for Hib and pertussis), and the testing can be expensive.

So we usually just do the testing (a quantitative titer) for folks that are in high risk situations, including:

  • pregnancy – rubella titer only (HBsAg is also done, but that’s not a vaccine titer test, but rather to see if you are chronically infected with hepatitis B)
  • healthcare workers – anti-HBs (antibody to the hepatitis B surface antigen to confirm immunity after being vaccinated)
  • students in nursing school and medical school, etc. – anti-HBs
  • children and adults exposed in an outbreakmeasles, chicken pox, mumps, etc., but only if we are unsure if they were previously vaccinated and protected
  • after a needlestick injury, etc. – to confirm immunity to hepatitis B
  • babies born to a mother with hepatitis B – to confirm that their hepatitis B vaccine worked

Vaccine titer testing might also be done for:

  • internationally adopted children – to confirm that they are immune if we unsure about all of the vaccines the child got in other countries
  • children and adults with lost vaccine records – to confirm that they are immune, since we are unsure about all of the vaccines they got
  • evaluation of children and adults with immune system problems – to help identify what immune system problems they might have – typically involves checking pneumococcal titers, giving Prevnar, and then checking pneumococcal titers again
  • people at continuous or frequent risk for rabies – rabies titer testing every 6 months to 2 years
  • patients with inflammatory bowel disease, before starting immunosuppressive therapy – hepatitis A and hepatitis B titers, as they might be at increased risk for hepatitis

While checking titers is easy, it is sometimes harder to know what to do with the results you get.

Of all of these different titers, only one tells you that you are immune due to vaccination.
Of all of these different titers, only one tells you that you are immune due to vaccination.

It is especially important to know that:

  • most people don’t need to have their titers checked routinely if they are not in one of the high-risk groups noted above
  • it isn’t practical to get titers tested as a method of potentially skipping one or more doses of your child’s vaccines, after all, if the titer is negative, then you are still going to have to get vaccinated
  • a healthcare provider with a negative measles titer after two doses of the MMR vaccine does not need another dose of vaccine
  • a healthcare provider who has anti-HBs <10 mIU/mL (negative titer) after three doses of the hepatitis B vaccine should get another dose of vaccine and repeat testing in 1 to 2 months – if still <10 mIU/mL, they should then get two more doses of hepatitis B vaccine (for a total of 6 doses) and repeat testing. If still negative, these documented nonresponders will need HBIG as post-exposure prophylaxis for any future hepatitis B exposures, but no further doses of hepatitis B vaccine.
  • vaccinated women of childbearing age who have received one or two doses of rubella-containing vaccine and have rubella serum IgG levels that is not clearly positive should be administered one additional dose of MMR vaccine, with a maximum of three doses, and should not be tested again
  • postvaccination titer testing is not recommended after the chicken pox vaccine
  • in addition to not being able to test titers for pertussis and Hib immunity, it is becoming difficult to test poliovirus type 2 titers, as the test uses a live virus that isn’t routinely available anymore (type 2 polio has been eradicated)

Still think you need vaccine titer testing?

More on Vaccine Titer Testing