Australia's rotavirus immunisation program: Impact on acute gastroenteritis and intussusception hospitalisations over 13 years

Background: Australia was one of the first countries to include rotavirus vaccines in its National Immunisation Program, in 2007. We compared trends in acute gastroenteritis (AGE) and intussusception-coded hospitalisations over 13-year post-vaccine period against five-year pre-vaccine baseline. Methods: In a descriptive before-after study, incidence of hospitalisations with ICD-code of rotavirus AGE (A08.0), other AGE (K52, A01-A09 excluding A08.0) or intussusception (K56.1) between 2002 and 2020 was calculated using population denominators by age and Indigenous status. We used 2002-2006 as pre-vaccine baseline and calculated Incidence Rate Ratios [IRRs] for 2008-2019 and 2020. Findings: In children aged <5 years, mean annual hospitalisation rate/100,000 decreased by 85% for rotavirus-coded AGE, from 248.3 in 2002-2006 to 37.6 (IRR 0.15; 95% CI 0.15-0.16) in 2008-2019 (61.4% for Indigenous children, from 680.2 to 262.2), and 46% for other AGE, from 1274.5 to 689.1 (IRR 0.54; CI 0.54-0.55), decreasing further in 2020 to 6.3 (rotavirus-coded) and 445.0 (other AGE). Rates for rotavirus-coded and other AGE declined in 2008-2019 in those aged 5-<20 years (IRR 0.52; CI 0.49-0.56 and 0.86; CI 0.85-0.87, respectively), but increased in 20-<65 years (IRR 2.38; CI 2.01-2.83 and 1.15; CI 1.15-1.16) and >= 65 years (IRR 2.24; CI 1.91-2.62 and 1.24; CI 1.23-1.25). Average annual hospitalisation rate for intussusception in infants was similar in pre-vaccine and post-vaccine periods (IRR 0.97; CI 0.90-1.04). Conclusion: Over a 13-year period post-rotavirus vaccine introduction we document major sustained declines in hospitalisations coded as rotavirus and other AGE in age groups <20 years, with no change in intussusception hospitalisation rates in infants. Despite small increases in AGE hospitalisations in adults, likely due to increased PCR testing, our findings are consistent with highly favourable risk benefit ratio at whole-of-population level in Australia.