The risk of intussusception with the Indian vaccine, Rotavac, is unknown [5]. The Rotavac vaccine has been introduced into the National immunization program of India in four states from 2016. In preparation for the introduction, the Indian Council for Medical Research (ICMR), which has been conducting surveillance for rotavirus disease [6,7], is planning to develop a safety and impact monitoring system.

The objective of this survey was to describe the capacity at hospitals participating in the ICMR's National Rotavirus Surveillance Network (NRSN)–which were originally selected to enroll children admitted with acute gastroenteritis to estimate the proportion of rotavirus positive cases–to conduct surveillance for intussus-ception. We also used available data to estimate the incidence of intussusception in children in infancy and up to 10 years of age.

The survey data was compiled and stratified by geographic region. The data from MOSC Hospital was summarized and stratified by age. Details of the population of the region around MOSC Hospital were obtained from the Demographic indicators report (2013), Government of India [8]. We estimated that 40% of the population uses the hospital for pediatric emergencies. The incidence rate of intussusception was calculated using total number of cases divided by total number of population at risk. A Poisson model was used to calculate the 95% confidence interval (CI).

Twenty-one (75%) of the hospitals in the network completed the survey. The key descriptors of each hospital are included in Table I. The data from the regions indicate that at least one hospital in the Southern (MOSC Medical College Hospital, Kolenchery; Om Hospital, Tirupati; and Christian Medical College, Vellore), Northern (St. Stephen's Hospital, Delhi) and Western (Kore Hospital, Belgaum; KEM Hospital, Pune; Lokmanya Tilak Municipal Hospital, Mumbai) regions of the country already have records available, and can record and analyze case data for sentinel surveillance of intussusception. In the eastern region, it should be feasible to establish surveillance at the Institute of Child Health, Kolkata in 2016. On the other hand, the survey data also established that some hospitals would be unsuitable for inclusion in a surveillance network because of the lack of availability of diagnostic and management facilities.

Table  I  Description of Selected Hospitals Participating in The National Rotavirus Surveillance Network 

Data from MOSC Hospital – which provides healthcare for over five million population from Ernakulam and Idukki district, Kerala, with an average of 3000 pediatric outpatient and 800 inpatients annually – showed that during the two year study period, there were 106 children (age <10 years) diagnosed with intussusception. The male-female ratio was 1.9:1. All 106 cases were diagnosed radiologically, and 96 (90.6%) were reduced by hydrostatic enema, while 10 (9.4%) required a laparatomy. None of the cases had history of receiving rotavirus vaccination. All children recovered.

The average incidence of intussusception in children <10 years was 29.8 (95% CI, 24.6 - 35.9) per 100,000 child-years, with the highest incidence (112.9 per 100,000 child years) in the 6-12 month age group (Table II).

TABLE  II	Estimated Incidence Rate of Intussusception Among Children (Age <10 Y) 
At Mosc Medical College Hospital, Ernakulam, Kerala, 2013-2015 

The survey of hospitals which were selected for inclusion in the NRSN for their ability to recruit children hospitalized with gastroenteritis showed that in major geographic regions of India, there are one or more hospitals that can also serve as sentinel facilities for intussusception surveillance. This is important because fewer resources will be required if the same hospitals can be used for surveillance for impact and safety when the rotavirus vaccine is introduced into the Universal Immunization Program.

Only a few hospitals within the rotavirus surveillance network were suitable for inclusion for monitoring of intussusception, and most smaller hospitals refer children that may require surgery. Management of intussusception at hospitals within the network is undertaken only at hospitals that have pediatric surgery services (Table I), even though reduction of intussusception is increasingly without surgery. Monitoring of intussusception, irrespective of when rotavirus vaccine is introduced, requires ensuring awareness and appropriate referrals among healthcare providers. Monitoring of the rate of intussusception following vaccine introduction requires preparation of hospitals to accurately record vaccination information for all cases of intussusception, which needs appropriate investment in training and data capture. All of these issues will need to addressed by the next iteration of the ICMR network, which is now preparing for both effectiveness and safety monitoring.

The background incidence rate of intussusception reported from MOSC Hospital is higher than the only other incidence data from India, which is from Delhi, and was based on two cases in the age group studied [9].

The limitation of the survey and this retrospective hospital-based study might be lack of quality of documentation, and incomplete clinical records. In terms of incidence, the rates may be under- or over-estimated depending on the proportion of the population accessing healthcare at MOSC Hospital. However, even at the highest rate of 113 in the 6-12 month age group in Kolenchery, these estimates are lower than reported for the whole period of infancy from other Asian countries such as Japan, Vietnam and South Korea, where the incidence of intussusception was 158, 296 and 326 per 100,000 child-years, respectively [10-12].

Overall, information on intussuception is needed, particularly when rotavirus vaccination is introduced, and the use of sentinel facilities will support safety monitoring post-vaccine introduction. However, promotion of awareness and rapid referral should be emphasized to ensure appropriate case management of intussusception. Careful recording of vaccination information will be needed to determine whether cases are in the risk window following vaccination or not, in order that vaccine associated risk is accurately estimated.

Contributors: MAM: collected and analyzed the data; SV: analyzed the data and wrote the first draft; GK, RA: designed the study, collected and analyzed data and revised the manuscript.

Funding: Indian Council of Medical Research.

Competing interest: RA heads the Epidemiology and Communicable Diseases Division at ICMR.