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With herd immunity. “Herd immunity” is a term that comes from cattle ranching. It means that almost all of the cows in a herd no longer can get a certain disease. Out in nature – out on the range — herd immunity develops for hoof and mouth disease after almost all the herd has caught hoof and mouth, and also lived through it. This herd is a lot smaller than the original herd (hoof and mouth disease is horrible) but almost all the remaining cows in the herd are immune.

They simply can’t get it again. Ever.

These cows are immune because they made antibodies in their blood to the hoof and mouth disease virus, while they were fighting it off. The antibodies block the virus. So, even if a new cow does come in sick with it, the hoof and mouth virus might make a few other cows sick – but it can’t really spread.

For people, and COVID-19, this pandemic will end either when we get natural herd immunity – or man-made herd immunity – herd immunity from a vaccine.

A vaccine that nearly EVERYONE now alive has to get – in order to develop antibodies to the COVID-19 virus.

In short, almost everyone now alive doesn’t actually have to eventually get COVID-19 – if scientists can develop a vaccine – and the sooner the better. Once enough people have been vaccinated, COVID-19 will be under control, because humans will have developed man-made herd immunity. Most scientists feel that developing an effective COVID-19 vaccine will take at least 1 year.

It’s likely it will take more than one dose of vaccine to make people permanently immune – like it does now, for polio or Hepatitis B, or HPV.


Probably. The air tends to be much dryer in the winter than in the summer.  In winter any droplets with virus in them get smaller and lighter quicker, as they evaporate,  so they travel further and stay in the air longer.

Warm, humid, summer air always makes it somewhat harder for a respiratory virus to spread.

The big question no one has the answer to yet is what is going to happen this winter in the United States.  COVID-19 could come back as bad or worse as the first time.  Or it might not come back much at all – or with a different severity.  But for right now, warmer weather should help.


To cut to the chase –  you are likely to be at least somewhat immune – doctors just aren’t sure HOW IMMUNE – and for HOW LONG.  And that’s critical.

In terms of HOW IMMUNE – For a few viruses – the most important is one called RSV  – you never get completely immune.  But every time you do get RSV gain,  it’s milder.  This is called partial immunity.

Most viruses that cause serious illness in humans confer total immunity.   Like hoof and mouth does in cattle.

Virologists are fairly certain – but not totally – sure COVID-19 will behave like those viruses – and not like RSV.

Now – as to HOW LONG – Two different coronaviruses with structures very similar to COVID19, called SARS and MERS, each had smaller outbreaks, earlier in the 2000’s.  People who got SARS and MERS very often  –  more often even than with COVID19 – got critically ill, and often died.   But SARS and MERS are much less contagious than COVID-19, so those coronavirus outbreaks were easier to contain, and did not turn into pandemics.

Folks who recovered from both SARS or MERS were highly immune to those viruses for at least 2 years after their illness.  At that point each outbreak had been controlled – natural antibody levels began to fall – and, basically, scientists lost interest.

So – we hope – natural immunity after infection for about 2 years – maybe longer.

We hope.  COVID19 is new –  and all viruses are different from each other – and we simply don’t know if it will follow the SARS/MERS  pattern.  Two is not a big series.

The good news is doctors should have a much better idea about antibody status and COVID19 immunity soon – likely within 6 months.   We’ll let you know. 

A vaccine will not be ready that soon.


Two main reasons.

1) People put out a lot of COVID-19 virus in the little drops of saliva everyone makes talking, for two days BEFORE they feel sick.  This is the major way COVID-19 is spread.  Doctors call this phenomenon  pre-symptomatic viral shedding.

Turns out, the duration of pre-symptomatic viral shedding is a very big deal when it comes to how easily viruses spread, since people generally don’t go out a lot, and mingle, after they feel sick.   But they sure do, before.

Most viruses shed pre-symptomatically for 12 to 24 hours.   COVID-19 – more like 2-3 days.

2) The COVID-19 virus itself is a beast.  People shed a lot of it.  And it survives for considerable periods of time in both in the air, and also on surfaces.


Social distancing isn’t anything new – when you know that you are sick with a cough and a fever you go lie down  – and if you can – you don’t go into work, and most people stay away from you.  And if friends or family are helping you, they try not to get too close – and you tell him to wash their hands.

This isn’t rocket science.

Until there is a vaccine, and artificial herd immunity, we must assume that everyone we meet could be infectious for COVID-19.

Remember!  COVID-19 is mostly spread by tiny droplets of saliva when we talk, as well as coughing and sneezing.   Unless someone is yelling or singing or coughing or sneezing – the droplets from talking don’t travel more than about six feet.


They’re much better than nothing.  A recent (04/20/2020) systematic review of the literature:  confirmed the obvious – masks lower infection rates by trapping the bigger, wetter droplets.  They don’t do much for the smaller droplets – there are plenty enough of those, too –  they’re the ones that travel up to six feet – but in previous viral outbreaks the folks who wore masks more often got fewer infections.

Protection wasn’t perfect, but wearing a mask helped.

There’s a reason why everyone working in an operating room always wears a mask.  And washes their hands before touching anything.  They don’t want to catch anything – or give the patient anything.