Active Versus Passive Immunity And COVID-19.
Right now more than 450,000 people worldwide have reportedly recovered from COVID-19, and that number keeps ticking up. That’s good news, of course; but just because someone has contracted and ultimately healed from the new coronavirus, doesn’t mean they’re entirely exempt from re-infection. That’s where the issue of immunity comes into play—and currently, researchers and scientists still aren’t sure what the body’s immune response to SARS-CoV-2 is, and how long it might last.
For the most part, the word ‘immunity’ conjures up thoughts of complete protection from an illness, but it’s much more complicated than that. Generally speaking, a person achieves immunity to a disease through the presence of antibodies, or proteins produced by the body that can neutralize or even destroy toxins or other disease carriers.
These are our ‘attack mechanisms’ against ‘invaders’. Those antibodies are also disease-specific, per the CDC—it’s why this year, for example, even if you got your flu shot, you have no immunity against the current coronavirus outbreak.
Past that, immunity itself can be broken down into two different categories: active immunity and passive immunity—and those differences depend on how the body was introduced to whatever virus or bacteria it developed antibodies for, and to what extent (and for how long) they can prevent future disease. The good news: Both types can play a role in future protection from (and even the potential treatment of) COVID-19.
What is active immunity and how is it acquired?
Active immunity results when exposure to a disease organism triggers the immune system to produce antibodies to that disease, and can happen one of two ways: Through infection with the actual disease, which is known as natural immunity; or through a vaccination (essentially, a killed or weakened form of the disease that won’t make someone ill, but will trigger the body to make antibodies), which is known as vaccine-induced immunity.
Active immunity that results from either situation—natural immunity or vaccine-induced immunity—will allow a person’s immune system to recognize the specific disease, if they ever come into contact with it again, which will then trigger the body to produce the antibodies needed to fight it off.
Active immunity is often longer-lasting and may sometimes even provide life-long protection—but that’s entirely based on the disease itself. Immunity to the varicella virus (aka, chickenpox)—either via acquiring the infection as a child or through a vaccine—can provide lifelong immunity or long-lasting protection for up to 10 to 20 years. Whereas a yearly flu shot must be repeated annually, as it provides the most protection within the first three months, and begins to lose most effectiveness after six months.
It’s also important to note that active immunity isn’t immediate—it can sometimes take several weeks to develop, which is why most doctors suggest getting your yearly flu shot by the end of October, in order to have protection by the time flu season begins to pick up in November or December.
What is passive immunity and how is it acquired?
While active immunity occurs when an individual produces antibodies to a disease through his or her own immune system, passive immunity is provided when a person is given antibodies. This can happen in utero or through antibody-containing blood products—such as immune globulin, or a substance made from human blood plasma—administered when immediate protection from a specific disease is needed.
The major advantage to passive immunity—and the reason why it’s sometimes used as a treatment against diseases—is that it provides immediate protection. But passive immunity doesn’t last as long as active immunity, and loses effectiveness within a few weeks or months.
Of course, this passive immunity may also be helpful when it comes to COVID-19—primarily through the potential use of convalescent serum or blood plasma collected from those who have previously recovered from COVID-19. This means giving antibodies from the blood of people who have recovered from COVID-19 to people who are actively ill in order to prevent complications and hasten recovery. But the use of convalescent plasma isn’t exactly new; it’s also been used as a treatment option in a variety of other infectious diseases, including Ebola, Middle East respiratory syndrome (MERS), SARS, and even the H1N1 and H5N1 infections. That may be a helpful treatment for those with critical cases of COVID-19.
Convalescent plasma as treatment for COVID-19 specifically is still being studied, and is not yet recommended as routine treatment—but while it’s not yet been approved for use by the US Food & Drug Administration, the FDA did provide guidance to health care professionals and investigators administering or studying the use of convalescent plasma for treatment of COVID-19, according to an April 13, 2020 press release.
Information courtesy of CDC and Health.com.
Limit your exposure to coronavirus by staying away from large groups of people and anyone who has recently traveled. Watch for symptoms such as low grade fever (Below 100 degrees), headache, dry cough, shortness of breath, and fatigue.
Click HERE for Florida Department of Health’s COVID-19 Data & Surveillance Dashboard.
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