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How effective are Rotavirus vaccines?
There are two FDA approved rotavirus vaccines available for use in the United States. These vaccines differ in how they are made and in the number of doses prescribed when they are given. Both are given orally and contain genetically engineered live attenuated human rotavirus strains or hybrid human-bovine (cow) reassortment rotavirus strains. Links to the rotavirus vaccine package inserts can be found on NVIC’s Rotavirus Quick Facts page.
According to the package insert1, RotaTeq vaccine will prevent about 74 percent of rotavirus cases, about 98 percent of severe cases, and about 96 percent of hospitalizations due to rotavirus.
No efficacy or safety information is available on the use of RotaTeq in immunocompromised infants as this was not evaluated in clinical trials. Safety and efficacy information is also unavailable for use of the vaccine in infants with a history of gastrointestinal disease, including those with chronic diarrhea, acute gastrointestinal illness, history of congenital abdominal disorders, abdominal surgery, or failure to thrive.
RotaTeq may not prevent diarrhea or vomiting caused by viruses other than the rotavirus strains covered within the vaccine.
According to the package insert2, from infancy through one year, ROTARIX efficacy against severe rotavirus gastroenteritis was 84.7 percent in infants who received two vaccine doses, and 81 percent among those receiving one dose. ROTARIX efficacy against hospitalizations for rotavirus gastroenteritis through one year was 85 percent in infants receiving two vaccine doses and 80.8 percent among those receiving one dose.
Two studies evaluated the efficacy of ROTARIX against all rotavirus gastroenteritis infections and against severe rotavirus gastroenteritis through two seasons. In the first study, ROTARIX efficacy was reported at 78.9 percent against all rotavirus gastroenteritis through two rotavirus seasons, but only 71.9 percent for cases occurring during the second season after vaccination. Against severe rotavirus gastroenteritis, ROTARIX efficacy through two rotavirus seasons was 90.4 percent, but only 85.6 percent for cases occurring during the second season after vaccination. ROTARIX efficacy in reducing hospitalizations for rotavirus gastroenteritis through two rotavirus seasons was 96 percent.
In the second study, ROTARIX efficacy was reported at 80.5 percent against severe rotavirus gastroenteritis through two rotavirus seasons, and 79 percent for cases occurring during the second season after vaccination. ROTARIX efficacy in reducing hospitalizations for rotavirus gastroenteritis through two rotavirus seasons was 83 percent.
The effectiveness or safety of administering ROTARIX to infants with chronic gastrointestinal disorders or in infants with known primary or secondary immunodeficiencies was not evaluated in clinical trials prior to licensing.
In the U.S., researchers have reported that rotavirus vaccines have decreased the number of rotavirus infections requiring medical attention. However, researchers also note that since vaccine’s introduction, the G12P rotavirus strain has emerged. While not directly covered by ROTARIX or RotaTeq, these vaccines appear to offer protection against the G12P strain in infants and young children. Additionally, since vaccine introduction, researchers have noted that epidemics of rotavirus are now occurring every two years.
In 2019, the Cochrane Collaboration published a system data review of the available rotavirus vaccines. This data review reported the following:
- In high mortality countries in the first-year post vaccination, ROTARIX vaccine was found to decrease the rate of severe rotavirus infection by 63 percent and severe all-cause diarrhea infection by 27 percent. In the second year, ROTARIX was found to decrease the rate of severe rotavirus infection by 35 percent and severe all-cause diarrhea infection by 17 percent. ROTARIX had no impact on reducing all-cause mortality rates in high mortality countries.
- In low mortality countries, ROTARIX vaccine was reported to decrease the number of severe rotavirus infection by 84 percent and severe all-cause diarrhea infection by 41 percent. In the second-year post-vaccination, ROTARIX was found to decrease the rate of severe rotavirus infection by 82 percent and severe all-cause diarrhea infection by 37 percent. After three years, ROTARIX did not reduce the rates of severe rotavirus infection but one study found a 27 percent decrease in all-cause diarrhea infection. ROTARIX had no impact on reducing all-cause mortality rates in low mortality countries.
- For RotaTeq vaccine, in high mortality countries in the first-year post vaccination, the vaccine was found to decrease the rate of severe rotavirus infection by 57 percent but had no impact on reducing the rates of all-cause diarrhea. In the second year, RotaTeq was found to decrease the rate of severe rotavirus infection by 41 percent and severe all-cause diarrhea infection by 15 percent. RotaTeq had no impact on reducing all-cause mortality rates in high mortality countries.
- In low mortality countries in the first-year post vaccination, RotaTeq was found to decrease the rate of severe rotavirus infection by 92 percent but no data was collected to determine the vaccine’s impact on all-cause diarrhea rates. In the second year, RotaTeq was found to decrease the rate of severe rotavirus infection by 82 percent but again, no studies looked at the vaccine’s impact on all-cause diarrhea rates. RotaTeq had no impact on reducing all-cause mortality rates in low mortality countries.
Following the introduction of the vaccine for use in infants, most studies reported that the use of rotavirus vaccines had resulted in declines of rotavirus gastroenteritis among populations for which the vaccine is not approved (i.e. adults and the elderly); however, a more recent study from Finland noted an increased rate of hospitalizations among older persons when compared to the pre-vaccine era.
In 2007, after the introduction and widespread use of ROTARIX in 2006, health officials from Brazil noted that:
“this vaccine appears less effective in preventing severe rotavirus gastroenteritis caused by PG2 strains, and immunologic pressure exerted by the vaccine may cause emergence of rotavirus genotypes that are not controlled by the vaccine. This possibility could change the pattern and distribution of the most prevalent rotavirus strains in the vaccinated population.”
Though their findings were criticized by the CDC and others, the study authors presented additional data to support their concerns and called for the need to further monitor rotavirus serotype circulation post-vaccination. A 2009 published study on rotavirus strain distribution in Brazil noted that the vaccinated children were less at risk for severe diarrhea caused by this strain but that the vaccination program needed to be continuously monitored due to the possible emergence of rotavirus strains not covered by the vaccine.
Surveillance of rotavirus serotypes in the United States following the introduction of RotaTeq found that G3 replaced G1 as the strain most frequently detected and that additional uncommon serotypes had also been detected. Additionally, by the 2007-2008 season, the mean age of rotavirus cases in children less than three years had increased significantly. The authors concluded that:
“These findings underscore the need for careful monitoring of strains to assess possible vaccine pressure-induced changes and vaccine effectiveness against various rotavirus genotypes.”
In 2018, the CDC published a report detailing three separate rotavirus outbreaks which had occurred in California in 2017. In their report, they conclude that while rotavirus vaccines were effective at preventing severe illness, they did not always prevent infection or protect against milder symptoms. They also noted that rotavirus infection does occur among adult populations and can spread quickly among persons living in a communal setting.
A 2018 Japanese study evaluating the effectiveness of rotavirus vaccines against an emerging strain of rotavirus (G8P strain) found that while the vaccines were effective against moderate and severe illness, they were not effective against mild illness during an outbreak of this unusual strain.
In 2020, researchers from Finland published a paper reporting that while high rates of rotavirus vaccination decreased the risk of disease, rotaviruses were still actively circulating. They reported that new strains of rotavirus had emerged, including a G12P, and stated that this
might be a potential alarm sign. They also noted that high vaccination rates will likely lower rotavirus disease rates, but that virus elimination will not be achievable.
Both RotaTeq and ROTARIX are live virus vaccines and it is possible for a vaccine recipient to shed the vaccine-strain virus to others. Persons most at risk for developing rotavirus through vaccine virus shedding are those who are immunocompromised and are exposed to a recently vaccinated infant.
In addition to vaccine virus shedding and transmission, infections from vaccine-derived strains can also occur. Vaccine-derived viruses are caused by a reassortment of the vaccine strain virus during its replication and elimination from the body. This type of rotavirus infection occurs when the genetic material in the rotavirus vaccine strains combine differently (reassortment) and create a new (novel) strain of the virus. This novel vaccine-derived virus is then eliminated from the vaccine recipient’s body (i.e bowel movement) and is transmissible to others and capable of also causing gastrointestinal illness.
IMPORTANT NOTE: NVIC encourages you to become fully informed about rotavirus and rotavirus vaccines by reading all sections in the Table of Contents, which contain many links and resources such as the manufacturer product information inserts, and to speak with one or more trusted health care professionals before making a vaccination decision for yourself or your child. This information is for educational purposes only and is not intended as medical advice.