COVID reinfections are possible. Should we worry?

Wow, another article telling us that reinfections are possible. Two days ago, the article told is there were 5 cases worldwide, now they're telling us its about a dozen.

Now they're telling us natural herd immunity is impossible and vaccines can offer us longer lasting immunity. I wonder how much funding these people are getting from big pharma. The wording of the article seems meant to get us to get the vaccine, perhaps every two years.

Anyway, as I have mentioned a number of times, those who recovered from the 1st SARS CoV (17 years ago) still have the memory lymphocytes that would protect them from a second attack. I suspect it will also be the case for SARSCoV2. The body does not continue to produce large amounts of antibodies after a month or so but maintain memory cells that can respond quickly and produce antibodies upon further contact with the antigen; that is very typical.

The examples mentioned above are very rare. And I wonder whether they were truly reinfections. Perhaps some of the first positive PCR results were false positives.

Humans do not retain immunity to seasonal flu or the common cold so why do you think humans will acquire permanent immunity to this corona virus?

Because highly pathogenic coronaviruses produce a much stronger immune response than the common cold, people still have reactive cellular immunity to SARS, many many years after the infection.

Influenza escapes immunity by changing the protein that is recognize by recombination, that is an advantage of being a virus with a segmented RNA that has endless variants around the world to mix, The SARS-CoV-2 don't have that advantage, it has changed enough to escape immunity exactly 0 times since it appeared last year. It is perfectly possible it will remain without doing it for much longer.

 Although immunity is acquired, as a rule, there are always exceptions.

Humans do not retain immunity to seasonal flu or the common cold so why do you think humans will acquire permanent immunity to this corona virus? We will probably need annual Covid shots along with our flu shots.

Have to agree with virusrex. Although immunity is acquired, as a rule, there are always exceptions. If one can acquire immunity with a high degree of certainty, that is as good as it ever gets.

Isn’t that normal logic, if you caught the virus and your body is weakened for weeks or months plus additional longtime side effects, then you are much more in danger with stronger symptoms and higher risks if you are infected again as soon as your immunity has sunk too quickly if there ever has been one. Come on, you know that all beforehand, don’t you?

reinfections may render the idea of herd immunity -- that is, a sufficiently high percentage of people eventually becoming immune to COVID-19 -- unrealistic.

Not really, every infectious disease have cases of reinfections, nothing in biology works perfectly all the time. Frequent reinfections are the ones that would be problematic, something that has not happened for the pandemic.

One patient was infected on 17 separate occasions over the study period.

"COVID-19 will probably behave the same," she told AFP.

That conclusion is not justified by her evidence.

It is well known that human coronavirus that produce mild disease are neutralized by broadly protective immunity that is short lasted, in a sense the body reacts in a moderated amount against an infection that is also quite weak.

The immunity produced by the highly-pathogenic coronaviruses is quite different, involves different mechanisms and can be very long lasting, at least in symptomatic patients.

On Monday researchers in the Netherlands released the case study of a 89-year-woman who died after contracting COVID-19 twice. She had been treated for cancer, and her immune system was damaged as a result, making her more susceptible to severe infection.

This is the most likely explanation, characteristics of the patients are much more common as a cause in reinfections than changes in the virus, if a new variant that can cause reinfections had appeared we would not see isolated patients being reinfected but clusters.

As the world searches for a vaccine, Iwasaka said that any eventually safe and universal inoculation would need to generate higher levels and longer lasting immunity in people than through natural infection.

Or the same levels even, if you compare the immunity produced by a vaccine against COVID-19 against the immunity produced by the natural infection by other human coronaviruses it is obvious you will get very different results, but that is because you are comparing oranges to apples.

It is extremely good that vaccines appear to offer long lasting immunity, but this may also be the case for natural infections that produced symptoms. People that never showed any symptoms may have only short lasted immunity (like the one produced by the other coronaviruses) but that is neither a fixed conclusion.

There is also the grim prospect of so-called antibody dependent enhancement -- when antibodies actually make subsequent infections worse, such as with dengue fever

No, not really, dengue fever is a very special case because it has four serotypes that variate just enough for antibodies to be useless for inactivation of the virus, but still attach to them and facilitate their entry to lymphocytes that are their primary target. SARS-COV-2 only has one single serotype identified until now (so antibodies present can neutralize them without problem), and their primary target are not the cells of the immune system. There is no reason to suspect ADE as a realistic possibility.

"The problem with coronavirus antibodies is that they wane so quickly and you can get reinfected with the same strain," she said. "So it could be that you need repeated (COVID-19) vaccinations all the time. This one will never go away. There is no way we can get rid of it. It will stay with us for the rest of humanity."

That depends on something that has been already disproved, immunity against highly pathogenic coronaviruses is not 100% dependent of antibody levels, but involves celular immunity as well. This cellular immunity is much longer lasted and depending on the vaccine it is also strongly stimulated, a person (naturally infected or vaccinated) can have no detectable levels of antibodies but still be protected from the disease for a long time.

Alternatively, it may have been a more virulent strain of the virus.

Although viruses usually tend to become less virulent with time, so my guess would be that his immune system was probably already compromised due to the 1st infection and the 2nd time around he just wasn't in as good shape to fight it as before.

Of course, this is just a layman's guess at best. Not attempting to declare anything here with any authority. Just guessing.