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Vaccines and Acetaminophen: Given Together?


Immunization has saved millions of lives over the years, and prevented hundreds of millions of cases of disease. In the United States today, children routinely get vaccines that protect them from 14 diseases, all of which, at one time or another, were a dangerous threat to our country’s children.

Diphtheria for instance,  used to be one of the most dreaded of childhood diseases, killing more than 10,000 Americans each year, but today’s doctors rarely ever see a single case.  Thanks to vaccinations,  smallpox, which was one of the most devastating diseases the world has ever known, has been erased from the Earth.  Most children do not have adverse response to vaccines, and for those who do, the reactions are usually mild, like soreness or swelling at the injection site or a low-grade fever.

By giving their children acetaminophen right before or after the vaccination, parents try to spare their children, especially babies, from the discomfort which is a practice recommended by some doctors. Czech scientists say that while acetaminophen could stop post-vaccination fever, it may also reduce the effect of the vaccine itself.     Roman Prymula, of the Czech University of Defence in Hradec Kralove and his colleagues, in hopes to determine the effect of acetaminophen on fever and on the immunogenicity of vaccines, conducted two randomized controlled trials;   one for the initial vaccine and one for the booster shot.  These trials included 459 healthy babies, 9 to 16 weeks old, who were getting regular vaccines against pneumococcal disease, Haemophilus influenzae type b (Hib), diphtheria, tetanus, whooping cough, hepatitis B, polio and rotavirus.

While half received only the vaccines, the others were also given acetaminophen every six to eight hours for 24 hours after vaccination.  The team discovered that babies given acetaminophen had a significantly smaller rate of fever after both the initial vaccine (42 percent vs. 66 percent) and the booster shot (36 percent vs. 58 percent).  According to the concentration of antibodies in their blood, the acetaminophen group also had a “significantly lower” immune response. However, when the researchers studied other vaccine data, they found that the effect of acetaminophen on antibody levels was much smaller when given after the vaccination when a fever had already developed.

Beginning in a killed or weakened form, vaccines are made from the same germs that cause disease.  After destroying the vaccine germs, the antibodies stay in your system and provide protection against the real disease, thus creating immunity, and a fever after a vaccine is a natural part of the body’s immune response.  The researchers note that because acetaminophen reduces the fever, and thus the interactions between immune cells, the body makes fewer antibodies, which would explain the reduced effectiveness of the vaccines in the long run.

“The interference of paracetamol (acetaminophen) on antibody responses could result from the prevention of inflammation,” the study authors wrote.  Another explanation in an editorial accompanying the study, Dr. Robert T. Chen of the CDC and colleagues proposed  “Despite being an inhibitor of cyclo-oxygenase 2 (COX-2), (acetaminophen’s) anti-inflammatory activity is contested, perhaps related to inhibition of activity in high-peroxide environments that are common at sites of inflammation.”   They wrote, adding that regardless of the device, the findings “present a compelling case” against the repeated use of acetaminophen during childhood immunizations.

This brings up a very important question: What about the H1N1 flu vaccine?   Dr. Marc Siegel, an infectious disease expert and associate professor of medicine at New York University School of Medicine in New York City, says that because the immune response from the H1N1 vaccine has been so robust, giving an infant acetaminophen before the shot “may not be a problem.”

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