Type of vaccines
Currently available vaccines protect us from diseases caused by selective pathogens: bacteria and virus. Vaccines are usually categorized based on the constituents of the vaccines.
1. Inactivated/ killed vaccine: Those vaccines containing killed pathogens or particles are killed/Inactivated vaccines. Even though they are killed, they can trigger immune reactions, hence protects from the targeted diseases in the future. e.g. IPV
2. Live Vaccines: Vaccines consisting of live strain of pathogens are live vaccines, however, they are attenuated or weakened to reduce their virulence or infectivity. They are not capable enough to cause disease but triggers immune response for future protection.
3. Toxoid vaccines: Some of the disease conditions are caused by toxins produced by the microorganisms rather than pathogens themselves. Eg. The symptoms of tetanus is caused by the toxins such as tetanspasmin, produced by the clostridium tetani. Those toxoid vaccines contain the treated toxins of the disease causing pathogens which trigger the immune system to produce antitoxins.
4. Subunit and Conjugate vaccines: Subunit and Conjugate vaccines contain only the certain components of the pathogens, for example vaccine against Hepatitis B virus contains antigens (protein structure) of the hepatitis b virus that incite the immune reactions against Hepatitis B virus. Some Subunit vaccines are produced with genetic engineering. Conjugate vaccines are unique and effectively powerful as the part of the pathogens are combined with carrier protein making them more effective.
| Vaccine | Targeted disease | Form | Type | Storage |
|---|---|---|---|---|
| Bacillus Calmatte Guerin (BCG) | Tuberculosis | Lyophilized powder , multi dose vial, requires reconstitution with diluent | Live attenuated ( They are live but weakened to reduce their infectivity or virulence) | 2 to 8 °C (As this is freeze-dried, hence recommended to store at -20C but no longer recommended) |
| DPT-HB-HIB | Diphtheria, Pertussis,Tetanus, Haemophilus influenza, Hepatitis B | Liquid, multi-dose vial | Combination of diphtheria toxoid, inactivated pertussis, tetanus toxoid, Antigen (HBsAg) | 2 to 8 °C (Don’t freeze) |
| OPV | Polio | Liquid, multi-dose vial | Live attenuated vaccine | Should be frozen at -14 °C in primary vaccine center but could be stored at 2 to 8 °C |
| IPV | Polio | Liquid, single dose vial/ multi-dose vial | Inactivated vaccine | store at 2 to 8 °C, don't freeze |
| Pneumococcal conjugate vaccine (PCV) | Diseases caused by Streptococcus Pneumoniae | Clear Liquid Suspension | Conjugate vaccine | store at 2 to 8 °C |
| MR (Measles-Rubella) | Measles and Rubella | Lyophilized powder, Requires reconstitution | Live attenuated | store at 2 to 8 °C |
| JE (Japanese Encephalitis)Vaccine | Japanese Encephalitis | Lyophilized powder, requires reconstitution, single-dose vial/ multi-dose vial | Live attenuated (Chengdu SA-14-14-2 strain) | store at 2 to 8 °C, should be used within 30 minutes of reconstitution |
| Td (Tetanus, diphtheria) Vaccine | Tetanus and Diphtheria | Liquid suspension | Toxoid Vaccine | store at 2 to 8 °C |
BCG
BCG is the abbreviated form of Bacillus Calmette Guerin. This vaccine is given for developing immunity against tuberculosis. In this vaccine, the strain of tuberculosis bacteria is live and attenuated, hence they are harmless and doesn’t cause disease but are active enough to induce immune reactions. This produces necessary antibodies and memory cells to protect against future potential tuberculosis infection.
DPT-HB-Hib
DPT stands for diphtheria, pertussis, tetanus. Previously, DPT vaccine contained only the antigens for DPT that protects against diseases, diphtheria (known as “Bhyagute rog” in Nepali), pertussis (known as “Lahare khoki” in Nepali), tetanus (known as “Dhanustankar” in Nepali). However, the vaccine is now pentavalent and protects the five diseases including Haemophilus influenza type b and Hepatitis B. Haemophilus influenzae is one of the common causes of the pneumonia in children in Nepal. It can also cause ear infections, meningitis.
Polio vaccines
There are two types of polio vaccines: Oral polio vaccine (OPV) and Inactivated polio vaccine (IPV). Inactivated (Killed) polio vaccine (IPV), containing killed pathogens, is developed by Dr. Jonas Salk. Albert Sabin is the developer of non-killed i.e. live oral polio vaccine which contains strains of weakened live polio viruses. When I had confusion regarding name of developers of live and killed vaccines, I used to remember by the work ‘k’ in Salk so he is the developer of killed polio vaccine and IPV is given by intramuscular route whereas live vaccine is administered by oral route.
MR vaccine
MR stands for measles and rubella. Previously, only measles vaccine was given to the Nepalese children. Later, Rubella has also been added to the EPI schedule of Nepal and MR vaccine is given subcutaneously at the age of nine months. MR vaccines protects children from diseases Measles and Rubella.
Pneumococcal vaccine
Pneumococcal vaccine is given to develop immunity against infection of streptococcus Pneumoniae.
Td Vaccine
Recently, Td Vaccine is prescribed to prenatal mother in Nepal. Td stands for Tetanus and the diphtheria. This vaccine contains chemically treated toxoids of tetanus and diphtheria that triggers the immune system to prepare for future potential toxin exposure.
JE vaccine
JE vaccine is given against the Japanese encephalitis. Japanese encephalitis is a mosquito borne (spread by mosquito bite) viral disease caused by infection of JE virus. Live JE vaccine is given in Nepal at the age of 12 months
It is always essential to check the manufacturer’s guide about storage and transport. Even though all the vaccines provide some level of protection against specific diseases, they are not free of adverse reactions so, it’s very important to inform vaccine recipients of all the anticipated adverse reactions. Here in my experience in USA, when I had to take the vaccines for compliance of vaccination as recommended by the university, I was given pamphlets related to vaccines and its adverse reactions and consented for the vaccinations and their unwanted reactions (a part of defensive medicine.).
See the immunization schedule of Nepal
By Pramila Rai
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