21 February 2021

Sunday morning reading

Here is my short version of this peer-reviewed review on immunity, vaccines and the covid. 

(for full article with Figures click here)

Any virus that can cause disease in humans must have at least one immune evasion mechanism—at least one immune evasion “trick.” Without the ability to evade the immune system, a virus is usually harmless. Understanding immune evasion by a virus is frequently important for understanding the (...) virus, as well as understanding challenges faced by the adaptive immune system and any candidate vaccine. In the case of SARS-CoV-2, the virus is clearly unusually effective at evading the triggering of early (...)immune responses (...). It is plausible that much of the nature of COVID-19 as an illness is a consequence of this one big trick of SARS-CoV-2.

In an idealized example of a (...) viral infection, the (...) immune system rapidly recognizes the infection and triggers  “alarm bells”(...). This can occur within a couple of hours of infection.

In a SARS-CoV-2 infection, the virus is particularly effective at avoiding or delaying triggering (...) immune responses (...)  enough to result in asymptomatic infection (...) or clinically mild disease (“mild” is a COVID-19 clinical definition meaning not requiring hospitalization).

If the innate immune response delay is too long—because of particularly efficient evasion by the virus, defective innate immunity, or a combination of both—then the virus (1) gets a large head start in replication in the upper respiratory tract (URT) and lungs, and (2) fails to prime an adaptive immune response for a long time, resulting in conditions that lead to severe enough lung disease for hospitalization (...). These factors can be amplified by challenges of age, as elderly individuals (...) struggle to make a (...) response quickly that can recognize this new virus.

Although lung infection is a major component of severe COVID-19 (and relatively slow), upper respiratory tract (URT) infection is important for transmission. Notably, a vaccine that can prevent severe disease, or even most URT symptomatic diseases, would not necessarily prevent transmission of virus. 

The elderly present particular and important challenges for COVID-19 vaccines. Older individuals are at much higher risk for severe COVID-19. 

One key feature of vaccines is that immunization occurs well in advance of infection, giving the adaptive immune system time to respond, expand, and mature. 

Overall, the interim results from the two COVID-19 RNA vaccine trials were virtually identical, with 94% and 95% efficacy and similar other outcomes. The safety profile of the two vaccines is also excellent, with a combined >70,000 doses administered and no serious adverse events. 

. . . the biggest unknown now is probably the durability of the vaccine-induced immunity. Because there is no licensed RNA vaccine, no clear reference point exists for how durable immunity will be for this vaccine. Are the antibodies durable? Is the T cell memory durable? Is the B cell memory durable? Those are all important questions, and it will take time to answer them.


am said...

Thank you for your summary, Sabine. I would not have been able to read very far into that entire article, although I did scroll down to the end and was rewarded with this:

"...In sum, there is no specific reason not to expect multiple other candidate COVID-19 vaccines to do well in humans now; although, of course, vaccine phase 3 clinical trial outcomes are notoriously difficult to predict. For the moment, it is a phenomenal accomplishment for the world to go from nothing to multiple vaccines with ∼95% efficacy signal ..."

Reading what I did read reminded me of my many years working as a medical transcriptionist where I transcribed information like this, understanding only a little of what I was transcribing but fully able to spell all the words, performing a necessary service in the medical world.

Ms. Moon said...

I know a woman who is posting every possible dreadful adverse reaction to the vaccine on FaceBook that she can find. Some of these led to death. And of course, there is always the claim that "they" (CDC, Governments) don't acknowledge these dreadful outcomes to the vaccine at all. I know that this isn't the point of your post in any way, but it disturbs me. It is also disturbing, of course, to think that we are accomplishing more with the vaccine than we are. What if this huge effort does not lead to any sort of long-lasting immunity? And yet, we must go down this road because what else have we got?
As the article said- it will take time to answer these questions.

Barbara Rogers said...

Thanks to both your post and am's comment, I am about to get my second Moderna vaccine next week, and being 78 with lung problems already, am especially interested in considering the length of protection from the vaccine. So though I might have 95% immunity for a while, apparently there are no long term effectiveness numbers yet...so I am glad I've gotten used to wearing a mask, and may just continue the rest of this year.

Sabine said...

You can create a similar list for many over the counter medicines. Just have a look at side effects of aspirin for a start - internal blood loss with potential fatal outcome is one.

37paddington said...

Thanks for sharing this. The durability of the vaccine immunity is indeed the open questions, as well as can the vaccinated still acquire the virus and spread it to others, while having mild or no symptoms themselves. Do you know the answer to this latter question? I haven't been able to find a definitive response.

Steve Reed said...

I've heard this too, that durability is the question. I suppose Covid vaccinations could turn out to be an annual event, like a flu shot.

Sabine said...

Early days.
As with so much about this virus, there is no definite answer yet.

Read here: https://www.nature.com/articles/d41586-021-00450-z

and here: https://www.sciencenews.org/article/coronavirus-covid-19-pfizer-vaccine-may-reduce-transmission

But note the wording, it's all based on suggestions, possible indications, maybe.

And nothing from peer-reviewed sources yet, just news outlets and editorials.
Maybe soon, keeping fingers crossed.

ellen abbott said...

thanks Sabine. this is kind of off topic but do you have any idea why no other RNA vaccines candidates have made it through the approval process? why these were successful?

Sabine said...

I am guessing that under previous conditions, i.e. without a pandemic, development of these types of vaccines was ongoing but lacking urgency as well as funding. There is a review in Nature from a few years ago praising this promising approach for cancer treatment and possibly infectious diseases and I think I remember to that there was an attempt of a vaccine when the Zika virus was almost reaching epidemic status in Brazil. There are definitely several more mRNA vaccines in the pipelines now. This research just got the boost of a lifetime.

Colette said...

Fingers crossed hoping for long protection, but time will tell. Thanks for this information.

Ms. Moon said...