Rotavirus Vaccine

Javed Ahmed
Rotavirus Vaccine - Introduction
Diarrhea is second leading cause of death only surpass by respiratory tract infections (RTI) and pneumonia, constituting 17% of all under five mortality world wide.(1,2) It is estimated that incidence of diarrhea in India is 1.71 episodes/ person /year in rural India and 1.09 episodes/person /year in urban India.(3)

Rotavirus is a wheel like icosahedral reoviridae double stranded RNA virus. It is subdivided into serogroup A-G and sub group 1 or 2. Group A rotavirus causes most of the human diseases. The outer viral capsid is made of protein VP7 (which determine G serotype) and VP4 (which determine P serotype). Each rotavirus is designated by G serotype and P serotype followed by P genotype in bracket e.g. G1P1A[8]. G1-4 and G9 are predominant 5 strains in USA and responsible for 90% of rotavirus gastroenteritis (RVGE). Out of these infecting strains, G1 causes 75% of disease. It is very stable and may remain viable if not disinfected. Rotavirus causes diarrhea in maximum among children in age 6-32 month and 13.3% of rotavirus infection involve children < 6 months. Rotavirus diarrhea is markedly seasonal in temperate climate with peak incidence occurring in the spring and winter season. (4) Rotavirus spreads through feco-oral spread, close person to person contact and by fomites.

It is estimated that rotavirus causes 160 million episodes of diarrhea world over in children < 5 years, out of which 25 million need outdoor visit, 2.5 million require hospitalization and 0.6 million succumb to it. That means a death due to rotavirus every minute. (4, 5) Thirty one -87% of health care associated diarrhea are rotavirus out of which one third are severe. The incidence is 0.3 to 4.8/1000 hospital day. (4)

In the Indian Rotavirus Strain Surveillance Network from 2005 to 2007, rotavirus was found in approximately 39% of 4243 enrolled patients. (4) In other study from Chandigarh, rotavirus constituted 11.5% (25/218) of total diarrheal episodes and 22 % (25/115) among the children affected with acute diarrhea. (6) In India rotavirus causes more than 1.2 lakhs deaths annually, 4.5 lakh hospitalization, 5 million clinic visits and 25 million diarrheal episodes in under 5 children.(4,5) Study has also documented earlier onset of rotavirus disease in India. Rotavirus shows marked seasonality in northern temperate climate but less seasonality in southern location with tropical climate. This is due to high circulation of virus in environment with children getting exposed at early age and contracting severe disease. The most frequent strain in India were mainly G2P[4] (25.7% of strain), G1P[8] (8.5%), G9P[8] (8.5%) in combination with other types.(4)

There is no difference in epidemiology of diarrhea, incidence is same in developed and developing nations. It spreads from person to person hence it is difficult to control through improvement of hygiene and sanitation alone. Difference lies in the outcome of severe diarrhea by rotavirus, chances of death by rotavirus diarrhea is only 1:50000 in USA as compare to 1:210 in developing countries due to lack of proper medical care.(5)

Two live oral vaccines are licensed in India and internationally.

- Human monovalent live attenuated vaccine derived from human rotavirus strain 89-12 grown in vero cell culture and contain G1P1[8] strain. (Rotarix by GSK)

- Human bovine pentavalent live vaccine which is five reassortants between the bovine WC3 strain and human G1, G2, G3, G4, and P1A rotavirus strain grown in vero cells. (Rotateq by MSD)

Both vaccines are highly immunogenic in developed nations with overall effectiveness of 75 -87% against any rotavirus diarrhea and 90-95% against severe RVGE. Monovalent Rotavirus Vaccine in developing countries (South Africa and Malawi) has demonstrated efficacy of 61.2% (44-73.2%) overall in developing countries. (11) Pentavalent vaccine has demonstrated efficacy against severe RVGE at 2 years of 48.3% (22.3-66.1%) in Bangladesh and Vietnam. (5, 12)

A placebo controlled monovalent rotavirus efficacy study done in India and serum anti-rotavirus IgA antibody were estimated Seroconversion rates were 58.3% (95% CI 48.7-67.4) in vaccinees and 6.3% (95% CI 2.5-12.5) in placebo. Seroconversion rates in the vaccinees were similar to that seen in Latin America study vaccinees which had shown 86% efficacy of the vaccine. (5)

Immunity against rotavirus is complex and involve both B cell (antibody mediated major) and T cell mediated (minor). It has been shown that serum anti IgA correlate maximum with protection but in absence of IgA, serum IgG is also protective. (13,14). Immunity is mucosal (local) as well as systemic. CD4+ T cell are also help in clearing the virus infections by helping proper induction of B cell response.

Monovalent live vaccine (RV1) is given orally in two doses minimum 4 weeks apart. It is provided as a lyophilized powder that is reconstituted just before administration. Each reconstituted 1 ml dose of vaccine contains at least 106 median culture infective dose (CCID50) of live attenuated virus G1P1[8] and no preservative. It can be given after 6 weeks and not after 12 weeks and completed prior to 32 weeks. Recently FDA has extended the deadline of first dose up to 14 weeks and 6 days. IAP recommends first dose at 10 weeks and second dose at 14 weeks due to interference with OPV.

Pentavalent live vaccine (RV5) (Rotateq by MSD) is given orally in 3 doses at age 2 , 4 and 6 months. First dose should be given between age 6-12 weeks and subsequent at 4-8 weeks interval. First dose can be extended up to 14 week and 6 days (recent FDA approval). All doses should be completed before 32 weeks.

In case a dose is missed, it is not necessary to restart the course but it should be completed within the time frame. In preterm stable newborn if he has completed 6 weeks, is clinically stable and discharged from NICU, Rotavirus Vaccine can be given.

Initial Rotavirus Vaccine was associated with intussusception and was withdrawn from market because of it. Incidence of intussusception is maximum around 9 months of age. Though newer vaccines are not associated with increased incidence of intussusception but their safety beyond 8 months is not proven due to lack of data hence it is not approved beyond 8 months. Initially Rotavirus Vaccine was licensed only up to 6 months of age, but with increasing usage and safety deadline was extended by FDA.

Rotavirus vaccines are stored at 2-8 degree C and is protected from light. Monovalent Rotavirus Vaccine can be stored at room temperature. Do not freeze the diluents or vaccine. Monovalent vaccine (RV1) can be administered within 24 hours of reconstitution, but pentavalent vaccine (RV5) should be used immediately after reconstitution.

Both rotavirus vaccines are safe and well tolerated with occasional vomiting, diarrhea. Intussusception incidence is not increased but caution is recommended in children with uncorrected congenital malformation of GI tract which predispose to intussusception. The vaccine is contraindicated in infant who has history of severe allergy (e.g. anaphylaxis) to Rotavirus Vaccine previously. Human monovalent vaccine oral applicator contains latex hence this is contraindicated in infant with severe latex allergy.

The vaccines should not be given in children with history of previous intussusceptions or immunodeficiency.

Readministration of vaccine is not require if infant spits, vomits or regurgitates during or after administration of vaccine though manufacturers of human monovalent vaccine recommend the dose may be repeated at the same visit. The infant should receive the remaining recommended doses as per routine schedule.

Ideally schedule should be completed with the same product. If previous product is unknown or was bovine pentavalent vaccine than total of three doses should be administered.

Rotavirus Vaccine Rotavirus Vaccine 01/10/2007
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