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Vaccines reduce Covid transmission by 40%: WHO (medicalxpress.com)
9 points by mdp2021 2 days ago | hide | past | favorite | 9 comments





> The World Health Organization's director-general Tedros Adhanom Ghebreyesus said many vaccinated people were wrongly thinking the jab meant they no longer needed to take any other precautions ... Data suggests that before the arrival of the Delta variant, vaccines reduced transmission by about 60%. With Delta, that has dropped to about 40%

> Of 845,000 sequences uploaded to the GISAID global science initiative with specimens collected in the last 60 days, 99.8 percent were Delta, according to the WHO's weekly epidemiological report. Maria Van Kerkhove, the UN health agency's technical lead on COVID, said the Delta variant itself was evolving

I was hoping for references to articles which better define those percentages, this is instead more of a reporting article about the WHO warning the public that vaccinated are not immunized* and do not cease to be vectors for transmission, hence the vaccinated should still take proportionate, appropriate precautions.

(*Though I read yesterday on El Pais that some actually immunizing vaccines should be on the way: https://elpais.com/ciencia/las-cientificas-responden/2021-11... . The article presented the information dashboard from the WHO about the different - over 300, a part of which non spike based (so quite different from the current ones) - vaccines against sars-cov-2 in development: https://www.who.int/es/emergencies/diseases/novel-coronaviru...)


Frequently in New Zealand we hear government and journalists suggesting vaccines affect transmission. In truth, masks affect transmission, jabs affect rates of hospitalisation. We had the impression early on that this would be like the measles vaccine, affecting spread. Not really true. There are other studies in Israel and the US showing no meaningful correlation between spread and vaccination rates.

For me the interesting question is: when vaccinated does exposure to COVID bump up our immunity so that we stay safe from serious illness long term, or will we forever be getting these vaccines (making the drug companies richer and richer)


Vaccines are supposed to affect transmission, but in a complex way: * reduction of chances of infection; * reduction of time of the being-contagious windows; * expelled virions covered with antibodies, making them less effective. If we add to that * reduction of the viral load, we arrive to a point that some took for granted at the beginning but that has been shaken recently. Good numbers, of course, to give a measure the effects (and of the effects in time, which studies have shown are being paramount in our context), are needed.

I find that, for example, the New Zealand Herald is very keen on dumb-level expression: even yesterday it could be seen following that setting (it made the usual statement of 'safe and effective' in the plainest way, which is childspeak and absurd).


I do wonder though about vaccines lowering symptoms and ‘disguising’ infection, thus potentially promoting spread

NZ Herald: a disgrace to the nation.


By the way: do you have links/references to those studies about the «correlation between spread and vaccination rates»?

> a disgrace to the nation

:) (If we could smile over these phenomena.) Do you have suggestions about good news and commentary sources in your area?

> vaccines lowering symptoms and ‘disguising’ infection, thus potentially promoting spread

I must note: the question about whether the vaccinated could have more asymptomatic cases is a very interesting intellectual proposal. In a way, factored by other effects (such as a reduced infection rate) it could be embedded in a measure of the complexive rates of being infective of the vaccinated. Policy wise though, it could be very relevant if the unvaccinated showed less symptoms.



I looked at that. If you assume that people in different areas behave in the same way with respect to social contact, even if they behave in different ways wrt. vaccination, then it supports your conclusion. The study tries to average that out, but...

There are studies that don't have this weakness. For example, you may look at households, on the assumption that people will have so much social contact with their households that the differences don't matter. Here's one that looks at that. "We estimated vaccine effectiveness against onward transmission by comparing secondary attack rates among household members between vaccinated and unvaccinated index cases, based on source and contact tracing data collected when Delta variant was dominant." https://www.medrxiv.org/content/10.1101/2021.10.14.21264959v... I've seen another study with comparable results (the error bars overlapped).


About news sources: some better than others but all highly deficient

> bump up our immunity so that we stay safe from serious illness long term

Two things (as laymen) could be noted: that rumour about vaccines immunizing from sars-cov-2 being on the way, and that this "historic episode" has boosted the research on coronaviruses themselves (which are normally something "undefeated").




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