Section II - Virology By Dr. Kareem Lilo
HPV is the most common sexually transmitted disease
Most people who are infected do not have any symptoms
Pap tests are performed on females to evaluate cells from the cervix under a microscope
- Cells are examined for abnormal changes that if left untreated may develop into
Figure(2-99)This woman has a skin rash from shingles.
Figure(2-100) This photo shows how influenza germs spread through the air when
Section II - Virology By Dr. Kareem Lilo
Figure (2-101)Head and shoulders of a boy with measles
Figure(2-102) This child is very swollen under the jaw and in the cheeks due to mumps.
Section II - Virology By Dr. Kareem Lilo
Causes severe vomiting and diarrhea that can lead to dehydration.
Dehydration can lead to death particularly in countries where medical care is not readily
Before there was a vaccine virtually all children had this infection by the age of five.
1. Protect the individual from disease.
2. Reduce the severity of disease.
Figure (2-104) This child was born with cataracts caused by a rubella infection his mother
.transmitted to him before birth
Section II - Virology By Dr. Kareem Lilo
4. Eradication of the disease.
History of vaccine development (Table 2-7)
In1796 Adward Jenner, used matter from cowpox pustules to inoculate patients successfully against
smallpox, which is caused by a related virus.
By 1900, there were two human virus vaccines, against smallpox and rabies, and three bacterial
vaccines against typhoid, cholera, and plague.
During the 20th century, other vaccines that protect against once commonly fatal infections such as
developed. The initial EPI goals were to ensure that every child received protection against six
they were one year of age and to give tetanus toxoid vaccinations
to women to protect them and their newborns against tetanus.
Since then, new vaccines have become available. Some of them, such as hepatitis B, rotavirus,
influenzae type b (Hib) and pneumococcal vaccines, are recommended by the WHO for global use.
Others, such as yellow fever vaccine, are recommended in countries where disease burden data
Section II - Virology By Dr. Kareem Lilo
Regulatory and safety issues of vaccines before and after licenses
The pathogens causing the vaccine-preventable are mainly microorganisms such as bacteria or
Bacteria are single-celled life-forms that can reproduce quickly on their own.
Viruses, on the other hand, cannot reproduce on their own. They are ultramicroscopic
infectious agents that replicate themselves only within cells of living hosts.
1800–1899 1900–1949 1950–1979 1980–1999 2000
Table (2-7) History of vaccine development
Section II - Virology By Dr. Kareem Lilo
Figure(2-106) Primary and secondary immune responses to the same pathogen
– Inactivated polio virus (IPV)
– Haemophilus infuenzae type b (Hib),
– Pneumococcal (PCV-7, PCV-10, PCV-13)
Section II - Virology By Dr. Kareem Lilo
Vaccines may be monovalent or polyvalent. A monovalent vaccine contains a single strain of a single
antigen (e.g. Measles vaccine), whereas a polyvalent vaccine contains two or more strains/serotypes
of the same antigen (e.g. OPV).
Some of the antigens above can be combined in a single injection that can prevent different diseases
or that protect against multiple strains of infectious agents causing the same disease (e.g.
combination vaccine DPT combining diphtheria, pertussis and tetanus antigens). Combination
children’s fear of needles and pain.
Available since the 1950s, live attenuated vaccines (LAV) are derived from disease- causing
pathogens (virus or bacteria) that have been weakened under laboratory conditions. They will grow
in a vaccinated individual, but because they are weak, they will Live microorganisms provide
continual antigenic stimulation giving sufficient time for memory cell production. cause no or very
Attenuated pathogens have the very rare potential to revert to a pathogenic form and cause disease
disease-causing vaccine-derived poliovirus (VDPV) associated with oral polio vaccine (OPV).
If the vaccine is grown in a contaminated tissue culture it can be contaminated by other
viruses (e.g. retro viruses with measles vaccine).
Many LAVs require strict attention to the cold chain for the vaccine to be are subject to program
failure when this is not adhered to.
Protein-based subunit vaccines
Section II - Virology By Dr. Kareem Lilo
- Protein based subunit vaccines present an antigen to the immune system without viral
particles, using a specific, isolated protein of the pathogen .
- Commonly used protein-based subunit vaccines are the following:
- Acellular pertussis (aP) vaccines contain inactivated pertussis toxin (protein) and may
contain one or more other bacterial components. The pertussis toxin is detoxified either by
treatment with a chemical or by using molecular genetic techniques.
- Hepatitis B vaccines are composed of the hepatitis B virus surface antigen (HBsAg), a
protein produced by hepatitis B virus. Earlier vaccine products were produced using
purified plasma of infected individuals. This production method has been replaced by
recombinant technology that can produce HBsAg without requiring human plasma
increasing the safety of the vaccine by excluding the risk from potential contamination of
Some bacteria when infecting humans are often protected by a polysaccharide (sugar) capsule that
helps the organism evade the human defense systems especially in infants and young children.
Polysaccharide vaccines create a response against the molecules in the pathogen’s capsule. These
molecules are small, and often not very immunogenic. As a consequence they tend to:
Not be effective in infants and young children (under 18–24 months),
Induce only short-term immunity (slow immune response, slow rise of antibody levels, no immune
Examples of polysaccharide vaccines include Meningococcal disease caused by Neisseria
meningitides groups A, C, W135 and Y, as well as Pneumococcal disease.
comparison to plain polysaccharide vaccines, they benefit from a technology that binds the
polysaccharide to a carrier protein that can induce a long-term protective response even in infants.
subunit vaccines, can therefore prevent common bacterial infections for which plain polysaccharide
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