Side effects are generally mild. It may cause mild pain and swelling at the site of injection and mild fever. More significant side effects are rare. Evidence is insufficient to link the vaccine to complications such as neurological effects. The vaccine should not be given to people who are pregnant or have very poor immune system function. Poor outcomes among children of mothers who received the vaccine during pregnancy, however, have not been documented. Even though the vaccine is developed in chicken cells, it is generally safe to give to those with egg allergies.