Rotavirus breakthrough infections responsible for gastroenteritis in vaccinated infants who presented with acute diarrhea at University Teaching Hospitals, Children's Hospital in 2016, in Lusaka Zambia

Abstract

Background Rotavirus has continued to affect under five children despite the introduction of the vaccine. This study aimed at characterizing the rotavirus genotypes responsible for diarrhoea infections in vaccinated infants aged 2 to 12 months and determined the relationship between rotavirus strains and the severity of diarrhoea in 2016. Materials and Methods We tested stool for group A rotavirus P6 antigen using an ELISA kit (ProSpecT TM , Oxford, UK). All positive specimens with enough sample were genotyped using reverse transcriptase polymerase chain reaction (RT-PCR). A 20-point Vesikari clinical score was used to determine the severity of acute diarrhoea. Diarrhoea scores between 1-5 were considered as mild, 6-10 scores were considered as moderate and scores greater or equal to 11 considered as severe. Results 153/424 (36%, 95% CI 31.5% to 40.9%) were positive for VP6 rotavirus antigen. The age specific rotavirus infections decreased significantly (p = 0.041) from 2 - 4 months 32.0%,followed by a 38.8% infection rate in the 5-8 months category and subsequently dropped in the infants aged 9-12 months with a positivity rate of 27.2%. 12.3% received a single dose of rotarix vaccine, 77.8% received 2 doses, and 9.9% were not vaccinated. 38.5% of those who received a single dose, 34.5% of those who received a complete dose and 45.2% of the unvaccinated tested positive for rotavirus. Infants who tested positive differed significantly from those who tested negative in terms of fever (p = 0.010).The predominant rotavirus genotypes were, G2P[6] 36%, G1P[8] 32%, mixed infections 19%, G2P[4] 6%, G1P[6] 4% and G9P[6] 3%. Infants who were infected with G1P8 and G2P[6] had a median Vesikari score of 6, while those who were infected with G1P[6] and mixed infections had a median score of 7 and those with infections due to G2P[4] and G9P[6] had median scores of 4 and 8 respectively. Discussion and Conclusion The breakthrough infection of heterotypic strains (G2P[6] (36%), homotypic, G1P[8] (32%) and mixed infections (19%) raises concerns about the effects of the vaccination on the rotavirus diversity, considering the selective pressure that rotavirus vaccines could exert on viral populations.