Two doses of the monovalent rotavirus vaccine (RV1, Rotarix, GlaxoSmithKline) is more than 90% effective at preventing severe rotavirus-associated gastroenteritis, putting the vaccine’s efficacy on par with the three-dose pentavalent rotavirus vaccine (RV5, Rotateq, Merck).
RV1 was licensed in 2008, two years after RV5, so uptake of the monovalent vaccine has only recently become widespread enough to enable formal testing of it’s performance.
“[Two] doses of RV1 and three doses of RV5 are both highly effective against rotavirus disease resulting in hospitalization or ED care,” Margaret M. Cortese, MD, of the CDC’s National Center for Immunization and Respiratory Diseases in Atlanta, and colleagues reported in Pediatrics.
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Before vaccines against rotavirus became available, it was estimated that nearly every U.S. child became infected with rotavirus by the age of 5 years, with most developing gastroenteritis.
To assess the effectiveness of the RV1 in relation to RV5, the researchers enrolled 593 children admitted to five hospitals in Georgia and Connecticut from January 2010 to June 2011 with acute gastroenteritis.
Acute gastroenteritis was defined as having three or more looser-than-normal stools in one 24-hour period and diarrhea onset within ten days of presentation. Participants were categorized as those who had received only the RV1 vaccine, those who received only the RV5 vaccine and those who had received a combination of the two.
There were a total of 165 rotavirus-positive cases and 428 rotavirus-negative controls. The two most prevalent rotavirus genotypes in the study population were G1P[8] and G2P[4].
For RV1, overall vaccine effectiveness (VE) for children who received the recommended two doses was 91%. Among children who received IV fluids, VE was higher at 95%, and rose to 98% among the subset of children hospitalized for gastroenteritis.
RV1 effectiveness decreased significantly for children who received only one dose, dropping to 53%.
Vaccine effectiveness was similar among children in the RV5 group and those who received a mixed dose series. Vaccine effectiveness was 92% among those who had received all three RV5 doses, and 95% among those who received a two-dose mixed series that included both RV1 and RV5.
Among all vaccinated children, those aged 12 to 23 months had a slightly better response to the vaccines than those aged 8 to 12 months, indicating that the passage of a few months after immunization might strengthen the immunologic response to either vaccine.
These results provide an affirmation of the success of these two vaccines, especially for RV1, which has been in circulation for a shorter period than its counterpart RV5.
Concerns over the monovalent vaccine’s efficacy arose after results from a previous clinical trial in Latin America indicated a relatively low 41% vaccine effectiveness against G2P[4] gastroenteritis — one of the most common rotavirus genotypes. In the current study, RV1 performed well against G2P[4] genotype, yielding 94% vaccine effectiveness against this genotype.
Moreover, the researchers “found no evidence of waning protection from RV1 through the second year of life,” an important distinction as “more than half of RV hospitalizations among children aged <5 years occurred after the first year of life.”
The study findings confirmed the effectiveness of RV1 and RV5, justifying use of both vaccines and supporting their continued use.
The CDC’s Advisory Committee on Immunization Practices (ACIP) currently recommends both RV1 and RV5 in the routine childhood immunization schedule. In February 2005, the ACIP recommended three doses of RV5 to be administered at ages 2, 4 and 6 months.
After RV1 received licensure in 2008, the ACIP recommended the two-dose series be administered at ages 2 and 4 months. For both vaccines, the first dose should be given at age 6 weeks through 14 weeks and 6 days, and the last dose given no later than age 8 months.
“Given differences in strain composition and administration schedule, understanding the effectiveness of both RV1 and RV5 in concurrent use is valuable,” according to the researchers.
by Walker Harrison, an undergraduate student at Columbia University and editorial intern with Clinical Advisor.
