Oral rotavirus vaccination had a strong protective effect against laboratory-confirmed rotavirus infection in the first 2 years of the U.K. infant immunization program, investigators are reporting.
CDC/Dr. Erskine Palmer
A transmission electron micrograph shows intact rotavirus double-shelled particles.
The estimated effectiveness was 77% for all infants with confirmed infection, and greater than 80% for those under 12 months of age, according to the report. The vaccine did not demonstrate efficacy against all-cause acute gastroenteritis, although this was likely because of high, sustained vaccine coverage coupled with the “substantial impact” of the rotavirus vaccine, wrote investigators led by Sara L. Thomas, MB BS, PhD, of the London School of Hygiene & Tropical Medicine.
Taken together, these findings provide “reassurance” that rotavirus vaccine is effective in a real-world setting and set the stage for future analyses of cost effectiveness, Dr. Thomas and coauthors said in a report on the study appearing in Vaccine: X, the open access mirror journal of Vaccine.
“As data accumulate in the post-vaccination era, more detailed assessment of waning of effectiveness over time can be undertaken, and investigation of rotavirus strain-specific protection,” they wrote.
Oral live-attenuated rotavirus vaccine (Rotarix) was introduced in the U.K. in 2013 as a two-dose schedule at 2 and 3 months of age. Vaccine uptake by the age of 25 weeks was rapid and sustained, exceeding 90%, according to previous reports. Declines in hospital admissions and primary care for all-cause acute gastroenteritis were substantial, associated with an estimated reduction of £12.5 million in health care costs in the first year of the program for children 5 years of age and younger.
To assess rotavirus vaccine effectiveness in the public health setting, Dr. Thomas and colleagues conducted a pair of studies: one designed to evaluate vaccine effectiveness against laboratory-confirmed rotavirus infections using laboratory surveillance data for 1,869 children and 1,032 controls and another to estimate vaccine effectiveness against all-cause acute gastroenteritis using electronic health data on 40,723 children.
Stratified by age, the data showed that vaccine effectiveness was 85% in those younger than 12 months, and 54% for older children.
By contrast, they found no evidence that the rotavirus vaccine protected against all-cause acute gastroenteritis in an analysis that adjusted for age and other factors. Analysis also suggested a lack of effectiveness against hospitalized acute gastroenteritis, according to the study authors.
In prelicensure trials, oral live-attenuated rotavirus vaccine in middle- and high-income settings had efficacy against severe rotavirus-confirmed gastroenteritis of greater than 85% and efficacy against severe all-cause gastroenteritis up to 40%, investigators noted.
The lack of vaccine efficacy on all-cause acute gastroenteritis is likely because of “highly effective implementation” of the vaccine program and rapid attainment of coverage, plus high vaccine effectiveness against rotavirus-specific acute gastroenteritis, the investigators said.
“As a result, almost all AGE in the study population in the post-vaccine era was likely to have been due to nonrotavirus organisms or non-infectious causes,” said Dr. Thomas and coauthors.
This highlights the importance of choosing “specific outcomes” to study when vaccine coverage and effectiveness are both high, they concluded.
Funding for this research came from the National Institute for Health Research Health Protection Research Unit in Immunisation at the London School of Hygiene and Tropical Medicine in partnership with Public Health England. The Immunisation and Countermeasures Division of Public Health England provided vaccine manufacturers with postmarketing surveillance reports, according to the article’s disclosure section.
SOURCE: Walker JL et al. Vaccine: X. 2019 Apr 11. doi: 10.1016/j.jvacx.2019.100005.