Sebb wrote: ↑Sun Sep 12, 2021 1:24 pm
Truedogz wrote: ↑Sun Sep 12, 2021 12:17 pm
Sebb wrote: ↑Sat Sep 11, 2021 11:47 am
ben475 wrote: ↑Sat Sep 11, 2021 11:39 am
who knows sebb, 70%? 80%? will the % start going backwards as the early receivers require boosters to maintain their fully vaccinated status?
Yeah true
Seb at this point the earliest recipients of Pfizer - frontline workers - will probably require boosters. At this point their protection is expected to be dropping by about 3-5% per month. As for the rest of us the jury is out. If as expected many in the population that are immunised become exposed to covid their immunity will be boosted. So how this plays out will depend on how widespread covid becomes here over the next 6-12 months. Other countries might impose a requirement for a booster before us travelling there. If they have a higher proportion of their population unvaccinated eg Israel they might do that for the protection of the vulnerable.
Israel right now are rolling out boosters not much to protect those already vaccinated but those that aren't. Looking at the latest projections it looks like we will get to 80+% vaccinated. But again protecting those that aren't particularly if there are distinctive pockets of them is going to be important.
This booster thing, is it similar to the flu shot that we supposedly to get every year?
Seb, well sort of.
Boosters are used for a range of reasons. One is when the vaccine used produce immune responses which decline significantly over time. This is determined by the type of vaccine, its immune mechanism and the type of pathogen. Some provide great long term protection eg 10 years while others are good for much shorter intervals. Think of tetanus that requires a booster every ten years. Another reason for a booster is to deliver an improved vaccine to counter new variants of a pathogen. This is what happens with influenza and could occur with covid but there is nothing on the horizon at this stages that warrants it.
There are range of reasons for immune response decline after vaccination. One explanation, of several, is that the immune response produced by a vaccine results in the production of 'memory cells' capable of recognising the same antigen and initiating an immune response. Over time these cells die. Once the specific memory cell levels become low the immune response is too slow to mount an effective defense. I'll try and dig up something on this for people to read. The evidence soon to be published suggests that protection from Pfizer falls away faster than that with AZ. This was predicted from theory based on the nature of the vaccines.
People exposed to covid, whether previously immunised or not, on the evidence coming through are mounting a much better immune response to re-exposure than those that haven't. Again there are various explanations one being that vaccines expose an individual to one component of the virus eg spike protein whereas natural infection exposes the person to all components. So far the evidence is while over time vaccines are declining in their ability to prevent re-infection they still provide excellent protection against serious illness and death.
Based on the Israeli experience if we want to maintain high protection of frontline workers from infection and passing it on to uninfected people they would start to need boosters around the end of the year. By that time we should have reached the 80% target and should not impact the rollout.