I'd assume that Canada and the UK followed a similar procedure in vaccinating their oldest first.
If the time between doses theory is correct, then the US should be seeing similar results to Israel in several months though there will be differences in that they have a higher proportion of their population with antibodies than we do.
I did have a look at a paper yesterday discussing the length of time between doses and it discussed the pros and cons of more time. The first dose does not provide great protection against Delta. The second dose does. If you wait a short time between doses, you get that high effectiveness in a short period of time but get waning protection down the road.
If you wait longer, then you get longer protection but your population is vulnerable in the time between doses and the two weeks to get to full vaccination.
It would appear that the ideal case would be to get two doses, spaced 3-4 weeks apart, and then another dose sometime after that.
Yes, all countries I’m aware of that have had widespread vaccinations have prioritized old folks into the first phase of vaccinations, followed by younger but high risk individuals. It only makes sense as they are most at risk. But again, older people have inherently weaker immune systems (a natural consequence of aging), not to mention are more likely to have conditions that weaken their immune system. If you give a vaccine to an old person (or person with weakened immune system), the immune response will not be as significant as a healthy, young person. So they’re less likely to have as many antibodies (and probably less likely to sustain adequate levels). It’s the same reason old people are less likely to have side effects from the vaccine.
I think it’s important that these breakthrough cases be analyzed taking into consideration age and pre-existing risk factors related to immune function. According to the CDC of 6500 breakthrough cases they observed, the median age was 58 and the IQR was 40-74 (median 50% of cases)… meaning 75% of the cases were over 40. Another study I saw say 75% are over 65. Maybe their age and underlying health status are a factor. Or maybe it’s because the majority of people not-vaccinated are young.
63% of the breakthrough cases were in women, interesting since females typically are better at fighting infection. Is that because they’re more likely to vaccinate (~5-10% more women than men, and more prevalent in older adults)? Or could it also be because women live longer and so more older women to infect?
Only 2% of these ~6500 died. The median age of death was 82 (IQR 71-89).
And this may seem silly but who knows if all of these patients were confirmed to have been vaccinated vs. just taking someone’s word for it. Unvaccinated patients coming into the hospital with COVID (or even
have been known to lie about getting the vaccine (or both shots), presumably to try an avoid embarrassment.
It’s also important to keep in mind a lot of these breakthrough statistics use positive results that do not differentiate between the delta variant and the older, less virulent strains. So we have to be careful to make assumptions about the delta variant.
In summary, looking at a lot of these statistics that get churned out lack context to really understand what is happening.
As of a few days ago a study found that 0.8% of breakthrough cases occurred in people who were fully vaccinated since January.
And in those breakthrough cases, the number 10% require hospitalization has been thrown around in the media. From the data I’ve seen, it’s actually more like 6-7%. The other 3-4% are asymptomatic but are hospitalized for another reason but discovered to have COVID while being admitted for some other medical reason.
You also see headlines about how the antibody levels in vaccinated people can decline 50% in a few months. This ignores the fact however that antibodies naturally degrade with time and the immune system does not continuously make high levels of antibodies for a pathogen it’s not actively fighting. We know more antibodies reduces risk of infection, but we don’t really know how much is enough and there are many other variables in play, like the quantity of viral exposure.
I imagine the CDC, pharmaceutical companies, and others are reviewing the utility of the third dose. If the data supports it, it’s likely adults 65+ or immunocompromised individuals received a third dose. I would imagine the rest of the population would wait until a new “booster” is created to cover the delta variant specifically, which will take some time.
This raises the ethical question of do you use vaccine on people who have already been fully vaccinated when much of the elder world population has not been vaccinated at all? Do you devote resources to producing a new vaccine to give to developed nations over underdeveloped? Will giving a 3rd dose in the US (especially when a sizable population is refusing to take the first dose/s as it is) save more people than getting poorer nations immunized?