INTERPRETATION Results indicate that vitamin D has a protective effect against RTI , and dosing once-daily seems most effective .
BACKGROUND Low levels of 25-OH vitamin D are associated with  respiratory tract infection ( RTI ) .
However , results from r and omized controlled trials are inconclusive .
Therefore , we performed a systematic review and meta- analysis to assess the preventive effect of vitamin D supplementation on RTI .
Vitamin D supplementation for severe pneumonia — A randomized controlled trial
Objective To determine the role of oral vitamin D supplementation for resolution of severe pneumonia in under-five children . Design R and omized , double blind , placebo-controlled trial . Setting In patients from a tertiary care hospital . Participants Two hundred children [ mean ( SD ) age : 13.9 ( 11.7 ) months ; boys : 120 ] between 2 months to 5 years with severe pneumonia . Pneumonia was diagnosed in the presence of fever , cough , tachypnea ( as per WHO cut-offs ) and crepitations . Children with pneumonia and chest indrawing or at least one of the danger sign ( inability to feed , lethargy , cyanosis ) were diagnosed as having severe pneumonia . The two groups were comparable for baseline characteristics including age , anthropometry , socio-demographic profile , and clinical and laboratory parameters . InterventionOral vitamin D ( 1000 IU for < 1 year and 2000 IU for > 1 year ) ( n=100 ) or placebo ( lactose ) ( n=100 ) once a day for 5 days , from enrolment . Both the groups received antibiotics as per the Indian Academy of Pediatrics guidelines , and supportive care ( oxygen , intravenous fluids and monitoring ) . Outcome variables Primary : time to resolution of severe pneumonia . Secondary : duration of hospitalization and time to resolution of tachypnea , chest retractions and inability to feed . Results Median duration ( SE , 95 % CI ) of resolution of severe pneumonia was similar in the two groups [ vitamin D : 72 ( 3.7 , 64.7–79.3 ) hours ; placebo : 64 ( 4.5 , 55.2–72.8 ) hours ] . Duration of hospitalization and time to resolution of tachypnea , chest retractions , and inability to feed were also comparable between the two groups . ConclusionS hort-term supplementation with oral vitamin D ( 1000–2000 IU per day for 5 days ) has no beneficial effect on resolution of severe pneumonia in under-five children . Further studies need to be conducted with higher dose of Vitamin D or longer duration of supplementation to corroborate these findings
INTERPRETATION Results indicate that vitamin D has a protective effect against RTI , and dosing once-daily seems most effective .
BACKGROUND Low levels of 25-OH vitamin D are associated with  respiratory tract infection ( RTI ) .
However , results from r and omized controlled trials are inconclusive .
Therefore , we performed a systematic review and meta- analysis to assess the preventive effect of vitamin D supplementation on RTI .