1 Department of Microbiology, Military Medical Academy, Cairo, 11291

2 Department of Gastroenterology, The Armed Forces College of Medicine, Cairo 11711

3 Specialist of Public Health, Ain Shams University, Cairo 11566, Egypt

4 Department of Parasitology, Faculty of Medicine, Ain-Shams University, Cairo 11566


A pathogen is a bacterium, virus, parasite or fungus that inhabits virtually every environment
on the planet and can cause diseases to man, animals and plants. Vaccines contain weakened or
inactive parts of a particular organism (antigen) that triggers an immune response within the
body. Newer vaccines contain the blueprint for producing antigens rather than the antigen itself.
Regardless of whether the vaccine is made up of the antigen itself or the blueprint so that the
body will produce the antigen, which will not cause the disease in the person receiving the vaccine,
but it will prompt the immune system to respond much as it would have on its first reaction
to the actual pathogen. They help to create protective antibodies-proteins help in fighting
off infections. But, vaccine refusal may result in vaccine-preventable disease in individual
and/or outbreaks of vaccine-preventable disease in unvaccinated and vaccinated individuals
However, severe allergic reactions to vaccines are rare but do occur. Local reactions involved
redness, swelling or irritation at the injection site. These common reactions typically begin
within a few hours of the injection and clear up soon after. Systemic ones, which are less common,
but potentially more serious develop sneezing, nasal congestion or hives or even throat
swelling, wheezing or chest tightness. Anaphylaxis is a rare life-threatening reaction to allergy
shots as low blood pressure and trouble breathing begins within 30 minutes of the injection, or
even starts later than that.
The vast majority of microbes are harmless, and many play essential roles in plant, animal
and human health. This overview focuses on immediate-type allergic reactions to human vaccines;
and delayed reactions are also briefly discussed overview discussed. The overview on allergic
reactions to the new developed parasitic vaccines will be given in due time elsewhere