乌鸦传媒

The development of a safe, effective rotavirus vaccine was a major milestone in reducing hospitalizations and deaths from the virus in children around the globe, but the rollout of the first rotavirus vaccine did not go smoothly.

A live, attenuated rhesus rotavirus-based tetravalent vaccine (Rotashield), developed in the 1990s by Wyeth Laboratories in collaboration with the National Institutes of Health, was shown to be highly effective and safe in preventing severe rotavirus disease in young children, and was licensed for use in the U.S. in 1998.

However, in July 1999, the CDC recommended that at least temporarily, based on reports to the Vaccine Adverse Event Reporting System (VAERS) of intussusception that were apparently linked to the vaccine.

"It was rare, but it was real," Paul Offit, MD, a physician in the Division of Infectious Diseases at Children's Hospital of Philadelphia, told 乌鸦传媒.

At the time, Offit served on the CDC's Advisory Committee on Immunization Practices. Ultimately, the committee withdrew its recommendation for the vaccine in October 1999 because of this safety concern. The effect of that decision resulted in Rotashield being withdrawn from use not only in the U.S. but around the world, Offit said, with potentially detrimental effects, especially in lower-income countries.

"I wish we hadn't taken it off the market, because even in this country, [children] were 5 to 10 times more likely to die of rotavirus than rotavirus vaccine-induced intussusception," he noted.

It would be another 7 years before the U.S. approval of another rotavirus vaccine.

The next two vaccines -- RotaTeq (Merck), a bovine-human reassortant pentavalent vaccine and Rotarix (GSK), a human rotavirus monovalent G1P[8] strain vaccine -- were held to even higher standards of safety during development, with trials enrolling more than 60,000 infants for each vaccine, Offit explained.

Although the trials showed that neither vaccine was associated with a greater risk of intussusception than placebo, when the vaccines were given to hundreds of millions of children, rare cases of intussusception did emerge. However, intussusception is also a of rotavirus infection.

RotaTeq received FDA approval in 2006 and Rotarix was approved in 2008.

How Effective Are the Vaccines?

The vaccines proved to be so effective that in the U.S., hospitalizations for rotavirus quickly became a rare occurrence.

According to the CDC, who receive the rotavirus vaccine series are protected against hospitalization from the disease and about 70% to 80% are completely protected from rotavirus illness.

Before the vaccine, rotavirus was the of severe dehydrating diarrhea in children in the winter months.

"I actually trained in the era when the rotavirus vaccine was being introduced," Brian Chow, MD, an infectious diseases physician at Tufts Medical Center in Boston, told 乌鸦传媒. "In the wintertime of my intern year, we would get like four or five admissions for each of our four teams per night for dehydrated babies, on bad days," Chow said.

"Fast forward to maybe about 5 or 6 years after the introduction of the vaccine ... we actually had the pediatric residents present a case of imported rotavirus," Chow commented. "The patient was from India and had not had a chance to be vaccinated against rotavirus. So the residents were all fascinated that there was a case of rotavirus gastroenteritis."

"Kids can get rotavirus vaccine and still maybe have some mild rotavirus, but it's something that parents can handle," at home, Robert Frenck, Jr., MD, a pediatrician and director of the Center for Vaccine Research at Cincinnati Children's Hospital, commented to 乌鸦传媒.

"What we really want is a vaccine that at least is keeping people out of the medical system so they don't get sick enough that they're needing to come to the doctor or to the ED or being hospitalized," Frenck said. "The rotavirus vaccine does an excellent job of that."

Are the Vaccines Still Linked to Intussusception?

The CDC states that there is a from rotavirus vaccination, usually occurring within a week after the first or second dose. This additional risk is estimated to range from about 1 in 20,000 to 1 in 100,000 infants in the U.S. who get the vaccine.

"But the virus itself also causes intussusception, and the critical question becomes what's happened since we basically replaced wild-type virus with vaccine virus," Offit commented.

In fact, from the CDC found that rotavirus vaccination was not associated with an increased 2-year intussusception risk among commercially insured U.S. children, and might even be associated with an overall reduced risk, since it prevents so many cases of severe illness.

"I don't think I have seen a single case of intussusception," in the post-vaccination era, Chow said. "I'd probably need to practice for several more decades seeing pediatric patients exclusively to see a case of rotavirus-associated intussusception."

According to the CDC, fewer children get the rotavirus vaccine compared with other childhood vaccines. Although full rotavirus vaccine-series completion is relatively high at 73%, it is lower than the 95% uptake of vaccines for diphtheria, tetanus, and pertussis.

showed rotavirus vaccination coverage rates were under 80%, suggesting rotavirus vaccines are underutilized relative to the Healthy People 2020 target and other childhood vaccines.

CDC Recommendations for Vaccine Administration

According to , the first dose of either the RotaTeq or Rotarix vaccine should be given before a child is 15 weeks of age. Also, children should receive all doses of rotavirus vaccine before they are 8 months old. Both vaccines are in liquid form and are administered orally.

RotaTeq, approved for infants between the ages of 6 to 32 weeks, is given in three doses at 2 months, 4 months, and 6 months of age. Rotarix, approved for use in infants 6 weeks to 24 weeks of age, is given in two doses at 2 months and 4 months of age.

Although infants who are mildly ill can receive the vaccine, it should not be given to those who are moderately or severely ill, including babies with moderate or severe diarrhea or vomiting. Vaccination can be considered in immunocompromised infants, such as those with HIV/AIDS, and those who are being treated with immunosuppressive drugs. Also, prematurity is not a contraindication to rotavirus vaccination.

Other contraindications to vaccination with rotavirus vaccines include severe allergic reactions to a previous dose of rotavirus vaccine or any component of the vaccine, severe combined immunodeficiency (SCID), or a previous episode of intussusception.

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