[pfg]

I don't understand how you came to that conclusion based on the articles you linked.

The first study finds that "The SAR [secondary attack rate] in household contacts exposed to the delta variant was 25% (95% CI 18–33) for fully vaccinated individuals compared with 38% (24–53) in unvaccinated individuals" and "Fully vaccinated individuals with delta variant infection had a faster (posterior probability >0·84) mean rate of viral load decline (0·95 log10 copies per mL per day) than did unvaccinated individuals with pre-alpha (0·69), alpha (0·82), or delta (0·79) variant infections." (The study did not determine a meaningful impact on peak viral load and on the SAR in households when the index case was vaccinated.)

The second link is a letter that reiterates the fact that vaccinated index cases are just as likely to infect other household members and concludes with "It appears to be grossly negligent to ignore the vaccinated population as a possible and relevant source of transmission when deciding about public health control measures", which makes sense, but does not mean spread

When you say "which is evident just by looking around what's going on everywhere", it's important to point out that we're now dealing with a variant that is significantly more transmissible than previous ones, so we can't compare the numbers like-for-like.

[spurgu]

> vaccinated index cases are just as likely to infect other household members

> It appears to be grossly negligent to ignore the vaccinated population as a possible and relevant source of transmission

You're going to have to dumb it down for me as to how this doesn't refer to spread.

> we're now dealing with a variant that is significantly more transmissible

And yes, agreed. Many are still focused on data from the previous variants though, whereas the thinking will need to change.

[pfg]

> You're going to have to dumb it down for me as to how this doesn't refer to spread.

Vaccinated index cases infecting others in the same household are only one scenario, and in that particular scenario, the study found no impact on spread. The study did find that vaccinated household members were less likely to be infected (SAR 25% vs. 38%) and that vaccinated cases had a faster rate of viral load decline - both of these findings (especially the first one) also relate to spread.

(It's arguably a bit surprising that the faster rate of viral load decline did not have an impact on the SAR for vaccinated index cases - one could make a (hopefully) reasonable hypothesis that this would matter more outside of household settings and thus still have an overall impact on spread, but that's not backed by any data from this study.)

There's also a world of difference between not "ignor[ing] the vaccinated population as a possible and relevant source of transmission" and saying that it doesn't stop spread to any significant degree. It's not binary.

[spurgu]

WHO is citing that study as well[0], seemingly drawing the same conclusion as I did:

> Prior to the emergence of the delta variant, it was reported that the risk of symptomatic cases in household contacts of vaccinated cases was about 50% lower than that among household contacts of unvaccinated cases(22). However, the impact of vaccination on reducing transmission in the context of the more transmissible delta variant appears to be lower(23).

https://www.who.int/news/item/24-11-2021-interim-statement-o...

[0] The first link I posted, reference 23 in the WHO statement

[pfg]

I'm really not sure if we're on the same page on the conclusion of the study, so I'll repeat it just in case:

Scenario 1: A vaccinated household member (the index case) is COVID-positive. The study finds that other household members are just as likely to get infected regardless of the vaccination status of the index case. There is no reduction of spread.

Scenario 2: Some household member (regardless of vaccination status) is COVID-positive. The study finds that other vaccinated household members are less likely to get infected. Spread is reduced.

That's basically what the WHO is saying - we may have had the positive impact of scenario 1 prior to Delta, but that's mostly gone. Scenario 2 still shows some effect on spread. It may be lower now, but it's still significant.

The article also states that "Vaccinating school-aged children may help minimize school disruptions by reducing the number of infections at school" and "there are benefits of vaccinating children and adolescents that go beyond the direct health benefits. Vaccination that decreases COVID transmission in this age group may reduce transmission from children and adolescents to older adults".