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.