The neutralizing antibodies (so-called because they stop the virus from being able to infect cells) can also be obtained from outside the body and can be given the recipients as a therapy for the prevention or treatment of a disease. Passive immunization is the process of administering the antibodies against a particular infectious agent.
An easy example is the antibodies against the rabies. In order to get immunity against rabies virus, we can receive rabies vaccine. Usually 2-3 weeks after the administration of the rabies vaccine (usually several courses), the neutralizing antibodies against rabies will develop in recipient’s body – this is called vaccine-induced active immunity. However, rabies antibodies can also be obtained from the human plasma donated by people in plasma collection centers scattered throughout the United States. The pooled plasma can be fractionated, and rabies antibodies can be obtained – these products are called RIG (Rabies Immune Globulin or hyperimmune globulin against rabies). The RIG can be given to the people to obtain so called ‘passive immunity’. If someone had potential exposure to rabies (for example, bite by wild animals) and had no record of rabies vaccination, the RIG should be immediately given to achieve the passive immunity for short period protection.
The same process of active immunity and passive immunity applies to the Covid-19 situation. Below is a table to compare the active immunity vs. passive immunity in Covid-19 situation:
Active Immunity
|
Passive Immunity
|
Relies on neutralizing antibodies against
SARS-CoV-2 (the virus causing Covid-19)
|
|
active immunity results when exposure to a disease organism triggers
the immune system to produce antibodies to SARS-CoV-2
|
|
Neutralizing antibodies are generated by our own immune system
|
Neutralizing antibodies are manufactured or obtained outside the body and then
given to the recipients
|
Active Immunity can be obtained in two ways:
Natural Immunity: obtaining immunity because of infection with Covid-19
(whether it is symptomatic or asymptomatic)
Vaccine-Induced Immunity: obtaining immunity by receiving the vaccine (vaccination)
that won’t make someone sick, but will trigger the body to make neutralizing antibodies),
which is known as vaccine-induced immunity
|
passive immunity is provided when a person is given neutralizing
antibodies.
Antibody-containing blood products: convalescent plasma obtained from
Covid-19 recovered patients
Hyperimmune products (containing concentrated neutralizing
antibodies)
Manufactured antibody products
|
It will take a while for the body to generate neutralizing antibodies
|
Off-the-shelf, ready to use
|
Immunity (once obtained) will be longer
|
Immunity will be shorter
|
Companies who are working on vaccines: see previous post “Coronavirus
Vaccine Tracker - Developing Vaccines Against Covid-19
“
|
Key players in the field (examples only):
|
Clinical trials in ‘healthy’ volunteers
|
Clinical trials in Covid-19 patients
|
Clinical trials to demonstrate the effect in prevention (prevent from
symptomatic Covid-19)
|
Clinical trials to demonstrate the effect in treatment (speed up the
recovery of the symptomatic Covid-19 patients and decrease the mortality)
|
The development process is longer
|
The development process is shorter
|
Larger sample size for clinical trials required for demonstrating the
efficacy in prevention of Covid-19
|
Smaller sample size for clinical trials required for demonstrating the
efficacy in the treatment of Covid-19
|
References:
- What to Know About Active Vs. Passive Immunity—And Why Both Matter With COVID-19
- Explainer: What are antibody therapies and who is developing them for COVID-19?
- A coronavirus vaccine is still months away, but an antibody treatment could be closer
- Coronavirus Antibody Therapies Raise Hopes—and Skepticism
- "Immunity passports" in the context of COVID-19
- CDC: Immunity Types
- CDC: Rabies
- China begins phase 1 clinical trials of neutralizing antibody treatment for COVID-19
1 comment:
Well said about Immunization
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