Vaccination vs hospitalisation

Today is Fathers’ Day and this picture reminds me of Dad, who died over 7 years ago. It is full of plants he particularly liked – snowdrops (Galanthus), two different types of hellebore, and Cornus Eddie’s White Wonder on the left of the picture, coming into bud. The snowdrops and hellebores are plants that we took from his garden.

The future is looking brighter for those outside Auckland, given that Ashley Bloomfield today talked about a new and improved COVID Alert Level 2 that will be proposed to Cabinet tomorrow. Cabinet will make its decision tomorrow afternoon as to what Alert Levels the country will be in when our current levels expire at midnight on Tuesday. Auckland will almost certainly have to continue to do the ‘heavy lifting’ for the country, given that there are still 20 new cases on each of the last two days, although only a small proportion of those were in the community while infectious.

My interest today is in the proportion of people who are hospitalised with COVID who have, or haven’t, been vaccinated. This information is unsurprisingly hard to come by. I assume it is being collected but, for some reason, it is not thought important to be distributed. You would think it very important for people to know if there is a strong link between vaccination and whether you get very ill with COVID, or not. Numbers of people getting very sick or dying is going to be the critical factor once COVID eventually becomes endemic in New Zealand; the numbers of people who will get very sick will be the factor around which the government makes decisions on vaccination levels and when we open up. I think it is important to note, however, that the point of knowing this information is not to criticise the specific people who have got sick and have not been vaccinated – it is quite possible they had no chance or were children who have no choice. This knowledge is about informing people’s forward decisions.

On 29 August it was reported that none of the 34 people hospitalised with COVID in New Zealand had been fully vaccinated and only 8 had received one dose (the number of people hospitalised is now at 38, 6 in ICU, 4 of those being ventilated). On 2 Sep we were also told that, of 687 people diagnosed with COVID in the current outbreak, 577 were unvaccinated, 82 had one dose and 41 two doses. And that’s the sum of total of the information currently available.

Australia is not doing any better than us on the vaccination-hospitalisation information front. I thought surely they would have some information, given the news that New South Wales hospitals are becoming critically full of people with COVID-19. The information may be out there hiding somewhere, but it isn’t hiding in plain sight that I can find (please let me know if you can). The only mention I found was in reference to a mistake made in reporting. Of 43 people hospitalised with COVID and in ICUs in Sydney on July 27, all but one were unvaccinated and the one had had a single dose. However, the inverse was reported, then corrected. The mistake was used by vaccine critiquers to ‘prove’ that vaccines are not useful.

Information I did find was a preprint of a paper from the United Kingdom, with figures on the effectiveness of vaccines preventing symptomatic disease, hospitalisation and death. Note that a preprint means a paper not been peer reviewed – there is a tricky nexus at present in terms of data needing to be available fast and peer reviews taking time. The data is for 14,019 cases of the delta variant, of whom 166, or 1.2% overall, were hospitalised. They don’t say how many cases of the alpha variant were recorded.

The table below shows the information on effectiveness of the Pfizer vaccine (as well as Astrazeneca). It uses three terms which I will explain here:

  • Odds Ratio (OR): the odds of something happening in one group vs another. The OR for someone with two doses of Pfizer not getting symptomatic delta is 0.12, or, 120 fully vaccinated people will get symptomatic delta compared with 1000 unvaccinated people in a population.
  • Hazards Ratio (HR): the hazards ratio is the comparative rate at which group A suffers something vs group B at a specific point in time. The HR for hospitalisation with delta if you get symptomatic disease and have had two doses of Pfizer is 0.34, or, you are 0.34 times as likely (2/3 less likely) to get hospitalised if you get symptomatic delta (you are already considerably less likely to get symptomatic disease).
  • Vaccine Effectiveness (VE): the proportion of people protected by a vaccine (note this is called ‘efficacy’ in clinical trials and ‘effectiveness’ for data from the community). VE is related to the number of people who get sick and the rate at which those sick people are hospitalised (VE = 1 – (OR x HR)). The VE for hospitalisation for two doses of Pfizer is 96% for delta, or, 96% of those who would otherwise have been hospitalised with COVID-19 will not be hospitalised. This one is really important – the VE does not mean that 96% of people won’t be hospitalised, it means 96% of those who have symptomatic disease and would otherwise have been hospitalised won’t be hospitalised.

You would have to say that this study suggests that having two doses of Pfizer vaccine significantly improves your chances of not getting symptomatic disease and hugely improves your chances of not being hospitalised. Another study published in the Lancet on people from Brazil and the UK found that, of nearly 12,000 people double dosed with Astrazeneca from April-November 2020, there was 95% vaccine efficacy and no-one was hospitalised. A study published in the Lancet on Israel found 97% vaccine efficacy against symptoms and hospitalisation and death, in a cohort where over 270,000 people got COVID-19 between January and April 2021. One proviso on all this data is that Israel is finding that vaccine effectiveness wanes after 6 months. Being vaccinated is still significantly more effective than not being vaccinated, but new figures are demonstrating the likely need for at least one booster shot and, as time goes on, we will find out when more boosters are needed.

I hope that our Ministry of Health will start providing us with some anonymised figures regarding the numbers of people in hospital with COVID who are or are not vaccinated. The MoH have slowly improved their reporting – at least they now tell us how many of the new cases are community cases, which they didn’t do until during this outbreak. However, their information and their display of it is woefully lacking. Information is power…those of us outside government would like some more power please.

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Published by janecshearer

I'm a self-employed life enthusiast living in Gibbston, New Zealand

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