Question

An infant receives her first dose of an oral vaccine.  The nurse explains to her parents that the vaccine is a weaken virus.  What type of immunity is being conferred on the infant?  What type of immunity did the infant from her mother in utero and when she was breast fed by her mother?  What classes of antibodies were given to her by her mother?

Answer 1

Vaccine provide active immunity in a newborn baby. Vaccines are suspensions of microorganisms that induce antibody production to protect against disease. It induces immunity in body.
In a newborn baby the weakened virus is introduced to produce the antibody against a particular pathogen in the blood so that the baby acquires an active immunity. e.g. POLIO VACCINE against poliomyelitis a common neurological paralytic disesase. It contians inactivated polioviruses. The weakened pathogen do not make the baby sick, but it can trigger the baby's immune system to believe that it has a disease so as to produce the antibodies against the disease. Thus the baby gets the immunity against this pathogen in the body to resist in a later time. This is how the vaccination works. The B lymphocyte will detect the antigen in the vaccine and react as if an infectious pathogen invaded the body. The inactivated pathogen or toxoid in a baby without a prior exposure of such antigen will stimulate the body to produce dominant IgM antibody initially followed by IgG antibody. There will be two or more booster dose needed.

In the foetus the passive immunity is transferred from the mother through the placenta in the form of maternal circulation antibody. This is passive because the antibodies are directly received by the host from mother. IgG antibody pass across the placenta and enter babies bloodstream and protect in uterus and also after birth during infancy. This is passive because the antibodies are directly entering into the fetal circulation.

The breast milk contains all forms of antibodies especially IgA antibody which induces a passive immunity in the baby's circulation. Breast milk also contains interferons which will protect the baby from viruses. There are a lot of white blood cells contained in colostrum- the first milk; which also contribute a passive immunity. This is a type of passive immunity.