Well explain. Maraming Salamat Doc.
Actually it is not the rain but it is the temperature. If it is too cold animals are susceptible to diseases and decrease immune response. Same as humans pag malamig prone tayo sa ubo at sipon. And when this happen the vaccine will not work on its full potential because most of the energy of the animal is being used to maintain its body temperature and not to elicit/produce immunity for the animal.