A lot of COVID-19 contrarians abuse the idea of "cross-reactivity" to make SARS-CoV-2 (the virus that causes COVID-19) look less dangerous than it really is. Many of them do this to avoid policies they dislike, like lockdowns.
Immune cells known as T cells and B cells have receptors that recognize viruses.
Think of the receptors as a lock, + portions of the virus as a key; i.e. the lock (receptor) binds to a specific key (virus region), + not to other keys
Even if you've never been infected with a virus, bacteria, etc., you almost certainly have T + B cells that recognize it.
When you're first infected, those cells (especially B cells) take a few days to increase in number (and activity) + generate their full immune response.
4/C
But if you're re-infected, T + B cells reach their full response quicker + better. That's what makes the T + B cell response *adaptive*; it improves w/ re-infection.
Vaccines typically work by mimicking a 1st infection, so u respond better later
One mistake involves non-experts messing up on terms like "immunity".
We immunologists can use those terms to mean generating a immune response, such as a T cell receptor binding a virus. That is not necessarily the same as being "immune" to infection, disease, etc.
9/C
Another problem is contrarians overlooking other impacts cross-reactivity can have.
Cross-reactivity from cold coronaviruses could be: 1) beneficial 2) useless 3) harmful
I've discussed elsewhere how cross-reactivity can be harmful.
Some core points:
- SARS-CoV-2 can exploit your immune response to make u sick
- immune response specific to a cold coronavirus could work badly on SARS-CoV-2
Cross-reactivity could instead be useless because:
- SARS-CoV-2 better evades the immune system than do cold coronaviruses [hence why SARS-CoV-2 is more deadly]
- the immune response to cold coronaviruses doesn't last long enough
Cross-reactivity might also be useless because infection with SARS-CoV-2 generates a different and *better* immune response to SARS-CoV-2 than does prior infection with a cold coronavirus.
Folks should also remember that SARS-CoV-2 managed to kill over a million people, even with cross-reactivity being present. So cross-reactivity clearly is not enough to prevent this virus from infecting and killing large numbers of people.
So beware if a non-expert tells you cross-reactivity is some saving grace from SAR-CoV-2, especially if that non-expert is politically-motivated to make SARS-CoV-2 looks less deadly in order to evade policies they dislike (like lockdowns):
Re: "COVID-19 contrarians abuse the idea of "cross-reactivity" to make SARS-CoV-2 (the virus that causes COVID-19) look less dangerous than it really is."
I'm fed up with politically-motivated non-experts (see part 7/C).
Thread on a myth Jay Bhattacharya (@DrJBhattacharya) continues to peddle to undermine confidence in public health agencies and to suit his policy agenda.
The myth may undermine responses to future public health emergencies.
Reporting systems are not perfect, so they sometimes miss infected people. That makes reported cases less than total infections, and thus CFR is higher than IFR.
The WHO was open about this since the early stages of the pandemic: