Author Topic: Having Covid-19 once might not give protection  (Read 181 times)

Offline Guy Etchells

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Having Covid-19 once might not give protection
« on: Saturday 30 May 20 06:54 BST (UK) »
There is a lot written about herd immunity and antibodies giving protection from a second infection, however very few mention that with a few diseases having once had an infection makes having a second exposure far more dangerous and sometimes fatal.

I must stress that this  antibody-dependent enhancement is not a common effect, but it can and does happen in a few diseases.

One such disease is dengue fever, scientists argued for years about whether a second infection would be worse than the first until in 2017 that American and Nicaraguan scientists published evidence which explained how antibody-dependent enhancement happened.

There is not room to explain what happens here but in brief it happens when the antibodies in a person drop to a low level, if the person is then exposed to a second infection the low levels of antibodies cannot neutralize or kill the invading virus but bind to them and effectively usher them into susceptible cells, where the viruses then replicate.

It is unlikely the this effect will apply to Covid-19 as it does not occur in earlier human coronavirus infections first identified the mid 1960s but the possibility is there until more is known and understood about this strain of the disease.

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Guy
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Offline sugarfizzle

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Re: Having Covid-19 once might not give protection
« Reply #1 on: Saturday 30 May 20 07:34 BST (UK) »
I thought we all knew that having had Covid-19 once might not give protection against a second infection. It has been stressed enough in the daily briefings and elsewhere.

However, your post suggests a similarity in some ways to how allergies are initiated. A first dose of penicillin is highly unlikely to cause any problems in somebody who later turns out to be allergic to it.  It is the second and any subsequent doses which cause the problem.

https://www.mayoclinic.org/diseases-conditions/penicillin-allergy/symptoms-causes/syc-20376222

"Before the immune system can become sensitive to penicillin, you have to be exposed to the medication at least once. If and when your immune system misidentifies penicillin as a harmful substance, it develops an antibody to the drug.

The next time you take the drug, these specific antibodies flag it and direct immune system attacks on the substance. Chemicals released by this activity cause the signs and symptoms associated with an allergic reaction.

Previous exposure to penicillin may not be obvious. Some evidence suggests that trace amounts of it in the food supply may be sufficient for a person's immune system to create an antibody to it."

Regards Margaret
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