Poor Ecuadorian older people suffer from chronic dietary deficiencies of zinc, iron, copper, vitamins C, B6, B12, D, and folic acid. The investigators have previously shown that these deficiencies are associated with impaired immune function and increased incidence of respiratory infections (RI). The hypothesis is that correction of these specific nutrient deficiencies will improve immune response and thereby enhance resistance to respiratory infections. To test this hypothesis this study will evaluate the effect of supplementation with specific vitamins and minerals found to be deficient in poor elderly Ecuadorians on markers of immune function and the incidence of RI. A randomized, double-blind, placebo-controlled trial in 320 older people (≥65 y)will be carried out in Quito, Ecuador. Participants will receive multivitamin and mineral supplements or placebo tablets daily for 12 months. Nutrients will be provided at US Recommended Daily Allowance (RDA) levels, except for vitamin C and zinc doses, which will be 5 times and 1.25 times higher than the RDA, respectively. Incidence of respiratory infections (the primary outcome) will be assessed weekly by field nurses and physicians from the study team. Secondary outcomes include delayed-type hypersensitivity (DTH) skin test, cathelicidin production by mucosa respiratory cells, and serum C-reactive protein (CRP) as measures of immune function. Blood micronutrient levels and haemoglobin status will be collected as measures of adherence to the trial regimen. Incidence rate of RI and rate ratio (RR) will be calculated to quantify the effect of the intervention on the incidence of respiratory infection. This will be the first trial of its kind conducted specifically in a population of older people known to have poor micronutrient status. The findings of the study may be important for similar populations in other low- and middle-income countries.