[рони]

face2005,

let current = parseInt($('#imunSistem .value').text(), 10), imunSistem = current;

$(function(){
    $('#vopros-1 input:checkbox').on("change", function(){
        imunSistem = current;
        $('#vopros-1 input:checkbox:checked').each(function(index, element){

                imunSistem += +element.value || 0;
            });
         $('#imunSistem .value').text(imunSistem);
    })
})