Today’s question is, why is there such a difference between the state of COVID infections in the United Kingdom and Israel? This question is related to my current personal question, which is, how long do I want to have between my Pfizer COVID vaccine injections? This latter question is something that anyone who isn’t yet fully vaccinated should be considering.
A couple of weeks ago I pondered as to why the numbers of COVID infections were dropping off in Britain, following ‘Freedom Day’. This week, there has been increasing news around the rapidly growing cases of COVID in Israel. I looked back at Britain to find that rates of infection are rising again. However, there is little parallel increase in hospitalisations or deaths – Wave 3 hospitalisations and deaths appear to be rising more slowly compared to infections, than in Wave 2. In contrast, in Israel the rates of hospitalisations and deaths are rising at the same rate in Wave 3 as they did in Wave 2.
So, why the difference? I went looking for articles on the internet and they were surprisingly hard to find. What I did find was that it appears that the Pfizer vaccine is far more effective at stopping serious illness and death than preventing infection. Pfizer is more effective at preventing illness and death than clinical trials predicted but less effective at preventing infection than trials predicted. This is a good thing in the sense that preventing serious illness and death is the ultimate goal.
What is harder to understand though is variation in the measured effectiveness of vaccines. A publication in the New England Journal of Medicine document that, in Britain, vaccines have been 88% effective against stopping symptomatic infection, while an Israeli Health Ministry study found that vaccines are only 40% effective. Both studies relate to cases of the Delta variant. So, which number is correct? Actually, both numbers could be correct because the situations in Britain and Israel are different:
- First we have to recognise the confounding factor that Britain and Israel have used different vaccines – in the UK older and other vulnerable populations received AstraZeneca, while younger people have received Pfizer or Moderna (both mRNA vaccines); in Israel everyone got Pfizer. However, the efficacy of mRNA vaccines has generally appeared higher than AstraZeneca in studies worldwide. I think though, it doesn’t do to discount any apparent links at present – I am always mindful of how the WHO proclaimed loudly that COVID-19 was not airborne in the early phases of the pandemic, and then has had to completely backtrack.
- Different time between exposure to Delta and vaccination: England vaccinated more slowly than Israel, with the majority of its population becoming fully vaccinated by mid-April 2021. In Israel, 90% of the most vulnerable were vaccinated by the end of January and most people by the end of February. It is becoming clear that vaccine immunity beings to wane noticeably from about 6 months – Israel has found effectiveness of the vaccine as low as 16% in some populations. If this is the driving force, then Britain’s hospitalisations might rise again in October-November if booster shots are not used.
- Different gap between vaccine doses used: the UK started off with 12 weeks between Astrazeneca doses and 8 weeks between Pfizer doses. Their approach was driven, in the first instance, by lack of vaccines and also the desire to get everyone with a first vaccine as soon as possible. There was some evidence for this gap, but initial trials did not focus on timing of doses – there are so many parameters to test in a trial, that they cannot all be done at once. Israel went with the gap initially recommended by Pfizer – 3 weeks, However, there is growing clinical evidence of greater immunity being provided by an 8 week gap. The British figures could be the real life, large scale example of such enhanced immunity.
In terms of my decision making as to when I should delay my second COVID shot to…we now have the complicating factor of COVID in the community. My best immunity will be two weeks after my second Pfizer dose (and it will inevitably decline from there) and the best dose spacing appears to be around 8 weeks. I want my immunity to last as long as possible, because I have a bad feeling that COVID-19 is now here to stay in New Zealand’s population. But I don’t want to be exposed to COVID until two weeks after that second dose.While Level 4 lockdown lasts I am all OK, because my chances of exposure are minimal. I could also do a voluntary, personal lockdown if Level 4 ends before my vaccine date arrives; however, that’s quite hard. How long could I isolate myself for?
My next dose is scheduled for next Friday (that’s 3 weeks after the initial dose)…I have 6 days to make a decision.
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