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Comment by jjuel | Hacker News Reader

This is what worries me the most. More research needs to be done, but if you can get reinfected it seems like herd immunity is a pipe dream. If immunity doesn't last long then does a vaccine even work? Now I am very clueless on all this so I could be way off. In fact if someone does know more about virology and could explain to me where I am wrong that would be great!

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If you get reinfected, can you expect the same level of severity? That's what I'm wondering. Does having antibodies for a a virus that's very close, but not quite exact result in less severe symptoms and/or a quicker time to showing symptoms? If so, that doesn't necessarily help the spread greatly right now, but it does point towards a time in the future where this virus actually is more like the regular colds and flus we are used to.

It maybe more that immunity within the body fades quickly, not so much that the virus mutates to the point it's different enough. The linked article talks about a sharp drop-off of coronavirus antibodies over time, which doesn't happen with antibodies for some other viruses (e.g. varicella antibodies are lifelong). And it doesn't sound like we really know why this might be.

Depends on the virus. For diseases like dengue you get antibody mediated enhancement of the infection, making it far worse, so the first time you're nearly asymptomatic and the second time you're on deaths door. For other diseases, even partial binding helps make the disease more mild. Biology is super variable.

For coronaviruses subsequent infections seem to be less severe. Some scientists speculate this coronavirus might not be intrinsically any more virulent than the 4 common cold coronaviruses, it's just that with this one we weren't able to train our immune system to handle it in childhood.

Well the article oversimplifies the linked source quite a bit in my opinion:

The article says

>Volunteers experimentally inoculated with HCoV-229E showed a steep decline in antibody response over time, and the majority could be successfully reinfected a year later.

while the linked source for that 1990 study says that while the 10 study participants were reinfected, none of them developed colds a second time, and the virus shedding period was much shorter.

Immunity will presumably last at least a few months, and the problem always reaches its greatest severity in the winter months because people are indoors more. We will just default to the influenza model, where there are circulating betacoronaviruses every season and we try to predict and vaccinate against them. The Middle East deals on and off with MERS.

Presumably immunity goes away once the antibodies are gone, but does the body remember the virus for next time? Assuming the virus does not mutate too much from year to year, at what point will it not be novel anymore to the human body? Will subsequent infections be easier for the body to fight?

From what I understand you build some resistance as you are exposed to multiple variants of the same flu virus so it's quite possible this would hold for coronavirus making refection less likely to lead to a severe infection.

Lets also not forget that there is likely to be well studied effective anti-virals at some point like we have for the flu today.

> If immunity doesn't last long then does a vaccine even work?

A flu shot-like regime would address this problem. If a vaccine is found, it won't be a vaccine you get once, but each year.

Well it makes it the same as the flu. We get a new vaccine every year that is slightly changed to match the dominant strain of the coronavirus.

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