Immunization against viral diseases

With the exception of smallpox, it was not until the 1930s that much began to be known about viruses and efficient viral vaccines became available. The two developments that contributed to the rapid growth in knowledge after that time were the introduction of tissue culture as a means of growing viruses in the laboratory and the availability of the electron microscope.

The first of the viral vaccines to result from these advances was for yellow fever, developed in the late 1930s. About 1945 the first relatively effective vaccine was produced for influenza; in 1954 there were introduced a vaccine for poliomyelitis; and in 1960 an oral poliomyelitis vaccine came into wide use. These vaccines went far toward bringing under control three of the major diseases of the time although, in the case of influenza, a major complication is the disturbing proclivity of the virus to change its character from one epidemic to another.

During the 1960s effective vaccines came into use for measles and rubella. Both evoked a certain amount of controversy. In the case of measles in the Western world it was contended that, if acquired in childhood, it is not a particularly hazardous malady and the naturally acquired diseases evokes permanent immunity in the vast majority of cases. Conversely, the vaccine induces a certain number of adverse reactions, and the duration of the immunity it produces is problematical. In the end the official view was that universal measles vaccination is to be commended.

The situation with rubella vaccination was different. This is a fundamentally mild affliction, and the only cause for anxiety is its proclivity to induce congenital deformities if a pregnant woman should acquire the disease. The consensus was reached that all girls who had not already had the disease should be vaccinated at about 12 years. In the United States children are routinely immunized against mumps, measles and rubella at the age of 15 months.

Answer the question: Why is an effective vaccine for influenza not available?

A. Because it can be acquired only in childhood;

B. Because the virus tends to change its character from one epidemic to another;

C. Because influenza is a fundamentally mild affliction;

D. Because the vaccine induces a certain number of adverse reactions.

Define the main idea of the text:

A. Changing character of influenza virus makes vaccination not very effective;

B. The introduction of tissue culture as a means of growing viruses caused a rapid growth in knowledge;

C. The major viral vaccines became available in the XIX^th century;

D. All girls should be vaccinated at the age of 12.

5. Read the following information and answer the questions:

a) Disinfectants kill microbes on surfaces.The most natural disinfectant is sunlight, but popular chemical disinfectants include carbonic acid, phenol, chlorine and iodine. Disinfectants work best on smooth surfaces like plastic, but they often do not kill all bacteria and those that survive an attack by chemicals will produce a resistant generation. Therefore, modern practice is to create conditions which discourage the growth of microbes rather than trying to kill them.

Question: What are the differences between disinfectants, antiseptics and antibiotics?

b) Quack doctor is a fake medical practitioner who claims to have miraculous cures and who sells medicines that are unproven and sometimes dangerous. Also known as ‘snake oil salesman’ (USA) because of exotic ingredients in the ‘cures’.

Question: Sometimes quack cures actually work. Why do you think this is?

Дата добавления: 2015-11-16