Contact immunity: Difference between revisions

Latest revision as of 11:53, 15 February 2025

An overview of contact immunity in the context of vaccination

Contact Immunity[edit]

Oral polio vaccine being administered, which can lead to contact immunity.

Contact immunity refers to the phenomenon where individuals who have not been directly vaccinated gain immunity to a disease through exposure to others who have been vaccinated. This occurs primarily with live attenuated vaccines, which contain a weakened form of the virus that can still replicate to a limited extent.

Mechanism[edit]

The mechanism of contact immunity involves the shedding of the vaccine virus by the vaccinated individual. This shed virus can then be transmitted to close contacts, who may develop immunity without having received the vaccine themselves. This is particularly relevant in the case of the oral polio vaccine (OPV), which is known to shed the attenuated virus in the feces of vaccinated individuals.

Examples[edit]

One of the most well-known examples of contact immunity is with the oral polio vaccine. When a person receives the OPV, the weakened virus replicates in their gut and can be excreted in their stool. In areas with poor sanitation, this can lead to the spread of the vaccine virus to others, who may then develop immunity to poliovirus.

Benefits[edit]

The benefits of contact immunity include:

Increased herd immunity: By indirectly immunizing individuals who have not been vaccinated, contact immunity can contribute to the overall level of immunity in a population, helping to prevent outbreaks.
Protection of vulnerable populations: Individuals who cannot be vaccinated due to medical reasons, such as immunocompromised individuals, may gain some level of protection through contact immunity.

Risks[edit]

While contact immunity can be beneficial, there are also potential risks:

Vaccine-derived virus: In rare cases, the attenuated virus from a live vaccine can mutate and regain virulence, leading to vaccine-derived infections. This is a concern with the oral polio vaccine, where vaccine-derived poliovirus (VDPV) can occur.
Unintended spread: In areas with inadequate sanitation, the spread of the vaccine virus can be uncontrolled, leading to potential health risks.

Related pages[edit]

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-'''Contact immunity''' is a type of [[immunity]] that occurs when an individual becomes immune to a disease after coming into contact with an infected individual. This can occur through direct contact with the infected individual or through indirect contact, such as touching a surface that the infected individual has touched. Contact immunity is an important aspect of [[public health]] and [[epidemiology]], as it can help to limit the spread of infectious diseases.
+{{Short description|An overview of contact immunity in the context of vaccination}}
-== Mechanism of Contact Immunity ==
+==Contact Immunity==
+[[File:Poliodrops.jpg|thumb|right|Oral polio vaccine being administered, which can lead to contact immunity.]]
+Contact immunity refers to the phenomenon where individuals who have not been directly vaccinated gain immunity to a disease through exposure to others who have been vaccinated. This occurs primarily with live attenuated vaccines, which contain a weakened form of the virus that can still replicate to a limited extent.
-Contact immunity occurs when an individual is exposed to a pathogen, such as a virus or bacteria, through contact with an infected individual. This exposure can stimulate the individual's [[immune system]] to produce antibodies against the pathogen, providing immunity against future infections.
+==Mechanism==
+The mechanism of contact immunity involves the shedding of the vaccine virus by the vaccinated individual. This shed virus can then be transmitted to close contacts, who may develop immunity without having received the vaccine themselves. This is particularly relevant in the case of the [[oral polio vaccine]] (OPV), which is known to shed the attenuated virus in the feces of vaccinated individuals.
-The exact mechanism of contact immunity can vary depending on the specific pathogen and the individual's immune response. In some cases, the individual may become infected with the disease but show no symptoms, a state known as [[asymptomatic infection]]. In other cases, the individual may experience a mild form of the disease before developing immunity.
+==Examples==
+One of the most well-known examples of contact immunity is with the oral polio vaccine. When a person receives the OPV, the weakened virus replicates in their gut and can be excreted in their stool. In areas with poor sanitation, this can lead to the spread of the vaccine virus to others, who may then develop immunity to [[poliovirus]].
-== Importance of Contact Immunity ==
+==Benefits==
+The benefits of contact immunity include:
+* '''Increased herd immunity''': By indirectly immunizing individuals who have not been vaccinated, contact immunity can contribute to the overall level of immunity in a population, helping to prevent outbreaks.
+* '''Protection of vulnerable populations''': Individuals who cannot be vaccinated due to medical reasons, such as [[immunocompromised]] individuals, may gain some level of protection through contact immunity.
-Contact immunity plays a crucial role in the spread of infectious diseases. It can help to limit the spread of a disease within a population by providing immunity to individuals who come into contact with infected individuals. This can be particularly important in settings where vaccination is not possible or not fully effective.
+==Risks==
+While contact immunity can be beneficial, there are also potential risks:
+* '''Vaccine-derived virus''': In rare cases, the attenuated virus from a live vaccine can mutate and regain virulence, leading to vaccine-derived infections. This is a concern with the oral polio vaccine, where vaccine-derived poliovirus (VDPV) can occur.
+* '''Unintended spread''': In areas with inadequate sanitation, the spread of the vaccine virus can be uncontrolled, leading to potential health risks.
-In addition, contact immunity can contribute to [[herd immunity]], a state in which a large proportion of a population is immune to a disease, thereby providing indirect protection to individuals who are not immune.
+==Related pages==
+* [[Vaccination]]
-== Limitations and Risks ==
-While contact immunity can be beneficial in limiting the spread of infectious diseases, it also carries risks. Individuals who become immune through contact with an infected individual may still carry the pathogen and spread it to others, even if they do not show symptoms. This can be particularly problematic in the case of diseases that can be spread through asymptomatic carriers.
-Furthermore, contact immunity is not always long-lasting. Depending on the specific pathogen and the individual's immune response, immunity may wane over time, leaving the individual susceptible to future infections.
-== See Also ==
-* [[Immunity (medical)]]
 * [[Herd immunity]]
-* [[Asymptomatic infection]]
+* [[Live attenuated vaccine]]
-* [[Public health]]
+* [[Poliovirus]]
-* [[Epidemiology]]
 [[Category:Immunology]]
-[[Category:Public Health]]
+[[Category:Vaccination]]
-[[Category:Epidemiology]]
-{{stub}}