Vaccines - Polio vaccine, HBV vaccine, Rubella, measles vaccine, JE vaccine
Introduction to Vaccines
Vaccines are medical products that are designed to stimulate the production of antibodies and provide immunity against one or several diseases in case of future infection. It acts as an antigen and is made from the parts of pathogens, its products, or is synthetically made.
There are numerous vaccines widely used throughout the world. These vaccines are targeted to contain or eliminate any infectious disease. Some of the commonly used vaccines include:
Polio vaccine
HBV (hepatitis B virus) vaccine
Japanese encephalitis (JE)
Rubella vaccine
Measles vaccine
Polio vaccine
There are two types of polio vaccine commonly used.
IPV (inactivated polio vaccines)- via injection in the leg/arm
OPV (Oral polio vaccine)- orally taken
IPV (inactivated polio vaccines)
IPV (inactivated polio vaccines) contains 3 poliovirus strains
Mahoney type 1
MEF-1 (Middle East Forces) type 2
Saukett type B
Polio viruses are either grown in Vero cells or Human diploid (MEC-5) cells, concentrated, purified, and then inactivated with formaldehyde.
OPV (Oral polio vaccine)
Viruses are grown in monkey kidney cells and continuous cell viruses (Vero or diploid cells). Polio SABIN vaccine is MgCl (Magnesium Chloride) stabilized preparation of live attenuated polioviruses of Sabin strain type 1, 2, and 3.
Each dose of OPV (Oral polio vaccine) also contains antibiotics (less than 25µg) such as streptomycin and neomycin. No adjuvants or preservatives are used.
Disadvantage of OPV (Oral polio vaccine)
OPV carries the risk of vaccine-associated paralytic poliomyelitis (VA-PP), particularly among infants. Vaccine viruses may revert back to wild-strain so vaccine-derivated poliovirus (VDPVs) may emerge. Thus, OPV (Oral polio vaccine) is soon to be discontinued.
Vaccination schedule
For children: mostly given when still a child and four doses of IPV (inactivated polio vaccines) are given at the following ages:
1st dose = 2 months
2nd dose = 4 months
3rd dose = 6-18 months
Booster dose = 4-6 years
For adults
It is mostly not required if they are already vaccinated as children. However, three groups of people are given due to a higher risk of infection:
people traveling to polio-endemic areas
lab personnel who handle specimens that contain poliovirus
Healthcare workers treating polio patients
1st dose = any time
2nd dose = 1-2 months after 1st dose
3rd dose = 6-12 months after 2nd dose
HBV (hepatitis B virus) vaccine
There are two types of hepatitis B virus:
plasma-derived vaccine
recombinant HB vaccine
Plasma-derived vaccine
These HBV (hepatitis B virus) vaccines are prepared from 22nm HBsAg particles obtained from the plasma of a person with chronic HBV infection. The virus is extensively purified and infectious particles are inactivated by several steps:
Aluminum phosphate or aluminum hydroxide is added to the vaccine as an adjuvant while thiomersal is used as a preservative.
It is not used now due to fears of transmission of blood-borne infections such as HBV and HIV and has been discontinued since 1992.
Recombinant HB vaccine
Recombinant HB vaccine uses HBsAg synthesized in yeast/mammalian cells.
Desired HBsAg gene is inserted in the plasmid and the such plasmid is inserted into yeast/mammal cells. The transformed cells are grown in large vessels as the HBsAg are expressed on cells. After purification, alum is added as an adjuvant, and the vaccine is obtained (dose = 2.5-40µg).
The vaccine is available in monovalent formulations or in fixed combination with other vaccines such as DPT, Hepatitis A, and IPV. At birth, if required only a monovalent formulation of the HB vaccine must be used.
Vaccination schedules
The minimum dose is at the interval of 4 weeks. More than 3 doses of the vaccine are not required.
For infant:
It is administered to those whose mother is HBV positive or unknown.
1st dose: birth
2nd dose: 1-2 months from birth
3rd dose: 6-18 months from birth
For adult:
1st dose: any time
2nd dose: 1 month from 1st dose
3rd dose: 5 months
About 90-95% of Hepatitis B vaccinated people develop an adequate immune response. It is age-specific, after 40 years of age, 90% of receptors required 3 doses and by 60 years, 75% only develop antibody titers.
Japanese encephalitis (JE) vaccine
Japanese encephalitis (JE) vaccines are of two types:
JE-MB
JE-VC
* (both have a dosage of 0.5ml)
JE-MB
Three doses of JE-MB are administered subcutaneously on days 0, 7, and 30. It is an inactivated vaccine prepared by inoculating mice intracerebrally (brain) with the JEV strain.
JE-VC
2 doses of JE-VC are administered intramuscularly 28 days apart
JE-VC is an inactivated vaccine derived from attenuated JEV strain propagated in Vero cells
The final dose must be completed 1 week before the potentially exposed
Vaccines should not be stored at 2-8°C i.e. should not be frozen and protected from light.
Rubella, measles vaccine
Rubella and measles vaccines are live attenuated measles vaccines derived from the Edmonton strain and are mostly used. They are also produced in chick embryo cells and human diploid cells. It may or may not contain small doses of antibiotics.
These vaccines are used mostly in two doses of 0.5ml at 9 months and 15 months by subcutaneous route.
Vaccinees can prevent disease but have no effect if a person is already infected. The second way of antiviral defense is antiviral drugs if the infection has already started.