Thursday, November 5, 2009

Tylenol and Vaccines

It seems like a lot of moms I know routinely give their kids tylenol either before or after their childhood vaccine shots, to make the experience a little less painful and keep fevers down. I've even heard of some pediatricians that in the past have told moms to give it. (Though my pediatrician never recommended it, I never heard any reasons not to use it). We'd been giving it to our daughter around shot time.

Well, recently a couple studies came out that reveal that tylenol decreases the response of vaccines by decreasing the antibody response, and the antibodies are why you want the vaccines--they are the how you end up being protected from viruses. After seeing what these studies show, I won't be using tylenol for my daughter's shots again! Here are the details, printed in the Lancet, arriving in my email from my journal watch service:

Prophylactic Acetaminophen Reduces Immunogenicity of Childhood Vaccines
        Children given acetaminophen with vaccinations have lower rates of fever in response, but the vaccinations produce a lower immunogenicity, reports a Lancet study.
Researchers, including some from the sponsoring vaccine manufacturer, followed over 400 infants receiving primary and booster immunizations. Half received acetaminophen via suppository in three doses over the first 24 hours after vaccination, and half received no prophylaxis.
        The percentage of children with a temperature of 38 degrees C or higher was significantly lower in the acetaminophen group by some 40% to 50% both at primary and booster immunizations. However, vaccine immunogenicity was lower in the acetaminophen group — significantly so for some antigens, e.g., all 10 pneumococcal serotypes after the primary immunization. The authors hypothesize that the effect could result from acetaminophen's preventing inflammation.
         Over 95% of all children had seroprotective antibody levels, but researchers argue that antipyretics "should ... no longer be routinely recommended" with vaccination. Editorialists agree, calling the case "compelling."

Acetaminophen After Vaccination Reduces Antibody Response

      Prophylactic doses of acetaminophen given after vaccination reduce fever but blunt antibody response to multiple antigens.
      Fever is common after vaccination, leading some to recommend prophylactic antipyretics. But do such agents affect vaccine immune response? In an industry-supported study, investigators randomized healthy infants in the Czech Republic to receive vaccines alone or followed by three doses of acetaminophen (suppositories) over 24 hours. They assessed febrile response and antibody response to vaccine antigens after primary and booster doses.
      The infants received 10-valent pneumococcal nontypeable Haemophilus influenzae conjugate vaccine coadministered with diphtheria–tetanus–acellular pertussis, hepatitis B, H. influenzae type B, oral rotavirus, and inactivated poliovirus types 1, 2, and 3 vaccines. Primary vaccine doses were administered at ages 3–5 months; booster doses at ages 12–15 months. Infants remained in the same group for primary and booster doses; however, based on initial results, the study was amended before completion, and not all acetaminophen-group infants received acetaminophen after booster immunization.
Fever >39.5°C was uncommon after primary vaccination in both groups (3/233 [1%] with no acetaminophen; 1/226 [<1%] with prophylactic acetaminophen). However, fever 38°C was significantly more common in the no-acetaminophen group than in the acetaminophen group (66% vs. 42%). Acetaminophen recipients showed significantly reduced antibody response to 10 pneumococcal conjugate vaccine serotypes and multiple other antigens. Children with and without fever in the acetaminophen group showed similar diminution of antibody response.
      Comment: The authors conclude that acetaminophen should not be given prophylactically as a routine practice with vaccination. Whether the same effect would occur with other commonly used agents, such as ibuprofen, is unknown but should be studied. The authors postulate that acetaminophen may interfere with interactions among dendritic, B, and T cells by reducing the local inflammatory response. Editorialists note the need to also assess whether antipyretics increase the proportion of vaccine nonresponders and reduce population protection.
No more prophylactic tylenol for our baby! At a later date I'll post about why we are not concerned about vaccinations and autism, and why kids should get vaccinated.