How Britain is balancing Covid and AstraZeneca risks

Also: Chechen bigamy and new forces of nature

In this week’s Hat Tip—

  1. Considering: UK limits AstraZeneca vaccine to over-30s

  2. News: Scientists suspect there’s a new force

  3. Curious: Chechnya leader’s two wives?

  4. Coming soon for subscribers: Labour Leader Kier Starmer’s first year

Considering: UK limits AstraZeneca vaccine to over-30s

The UK today decided to limit the AstraZeneca coronavirus vaccine to people over the age of 30, after reviewing the evidence of an extremely rare (four in a million) but serious side effect: cerebral venous sinus thrombosis, blood clots in veins in the brain.

The vaccine, which is often called the “Oxford Vaccine” in the UK and now Vaxzevria in Europe, has been controversial for months. US regulators didn’t like the Phase III trial design, and Germany originally limited it to younger people because there were very few over-65s in the study.

But the AstraZeneca vaccine also has a lot of benefits over other options: it’s cheaper to produce, stable for months in a normal refrigerator, transports well and the company is selling it at cost, giving up profits to help the world. The Pfizer and Moderna vaccines, by contrast, need to be stored at -20C and can’t be bumped once mixed. This makes the AstraZeneca vaccine especially useful for remote places with less medical equipment, or for home visits.

The risk

There had been a few reports in Europe of these rare blood clots being associated with the AstraZeneca vaccine, some of which might have even led to death. Even now, it’s hard to know for sure what’s causing the clots, but there’s at least some evidence that it’s the vaccine.

The UK’s government scientific advisors estimates that the chance of the vaccine causing cerebral venous sinus thrombosis (CVST) is about one in 250,000. That’s very rare; so rare that no clinical trial would ever have found it because it would need to have millions of people in the test.

But that’s not the whole picture. It seems like CVSTs are more likely to happen in younger people (eleven in a million chance for under-30s) and less likely in older people (two in a million for over-60s). There are also more observed cases in women, but that could just be due to more younger women having been vaccinated first; there is no evidence yet that women are at higher risk.

At a press conference on Wednesday, Jonathan Van-Tam, England’s deputy Chief Medical Officer, explained the thinking.

Comparing risks

Basically, the risk to not getting vaccinated depends on two variables: your chance of catching the coronavirus, and your risk of getting seriously ill with Covid-19 if you do catch it. Multiply these together and you have your risk of serious illness overall.

Age is the biggest factor in determining the risk of serious illness and death among people who catch the virus. Older people get sicker, have more serious symptoms and are much more likely to die than younger people. The CDC estimates that a 40-49 year old has 130 times the risk of Covid death of a young teenager; someone in their 90s has 8700 times the risk!

Other things get thrown in here too, like pre-existing medical conditions and the state of the healthcare system that would care for you if you were seriously ill.

The chance of catching the coronavirus, though, depends on the prevalence of the virus. During a Covid wave, more people have the virus and so you’re more likely to be around infected people. Another factor here is whether the variant spreading in your community is more infectious, and of course individual lifestyle and behaviour matters too.

So the risk to not getting vaccinated changes according to how much Covid is out there where you live. More cases means more virus, more virus means more risk.

This is an important part of the calculation that the UK is making. Right now Britain has been in lockdown for months, and a frighteningly-high Covid wave has finally collapsed. Incidence is down a lot. The risk of someone under 30 catching the coronavirus in the first place and then ending up in the ICU is now very very low; lower, in fact, than the roughly 11 in a million risk from the vaccine.

The diagram above tells the story well. Even with low incidence, people 30 and older are clearly safer vaccinated with an AstraZeneca vaccine than nothing. But for the under-30s, the balance of risk is less clear, with the one-in-100,000 chance of a dangerous side effect pretty similar to the risk of serious Covid.

Now, this doesn’t include every risk. Even mild Covid can cause long-term health conditions, including lung damage, other organ damage and the various syndromes known as Long Covid.

It also doesn’t take into account the social benefits of being vaccinated, most importantly that a vaccinated person is much less likely to catch the virus and spread it to others. It’s purely comparing the personal risk of ICU admission to the risk of CVST.

The UK has Pfizer vaccines and Moderna stock on the way, which made this an easier decision. Instead of stopping vaccination for under-30s, they’re able to just switch who gets which jab, giving the AstraZeneca doses to older people who are both less at risk of CVST and more at risk from Covid.

Other countries

However, if the virus was a bit more prevalent in the UK, the calculations might have been different. Here, with 60 daily infections per 100k people, the AstraZeneca vaccine becomes clearly safer than no vaccine at all, despite the CVST risk.

Many countries have virus rates at this level or higher. France is in a huge wave right now and Canada’s graph, while much lower, is almost vertical.

So while the UK has made a decision to give younger people alternative vaccines instead of AstraZeneca, that might not be the right option for other countries, where the Covid risk itself is higher.

Lots of drugs have serious and life-threatening side effects. Mass vaccination means millions of people getting the same drug in a short time, making ultra-rare side effects more visible due to scale. Ultimately, that’s a good thing. The fact that we have more than one vaccine available is even more amazing, allowing scientists to give people the best, safest vaccine for their age as more stock becomes available.

In the short term, though, we’ll have to see if there’s a panic about the AZ vaccine despite the four-in-a-million risk to adults as a whole. For now, the UK media is actually behaving fairly responsibly and I’m oddly optimistic that by being honest about the risks and balances, the government has done the right thing.

News: Scientists suspect there’s a new force

French Astronomer Urbain Le Verrier was already famous for discovering the planet Neptune. In 1859, he started to work on a different problem. He carefully tracked the movement of the planet Mercury, and noticed it wasn’t moving how it was supposed to according to Newton’s equations. The problem of the perihelion precession of Mercury bothered Le Verrier a lot; his best theory was that there must be a hidden planet exerting a gravitational pull too. Le Verrier called the hypothetical planet “Vulcan”.

It took until 1915 for Albert Einstein to find the real answer: Newtonian physics was incomplete and the world was weirder than it seemed; he proposed a new theory of General Relativity.

Something similar might have just happened. Scientists have found an interaction between quantum particles called muons that seems to be stronger than it should be.

The Standard Model of Quantum Physics says there are four fundamental forces in the universe: gravity, electromagnetism and the strong and weak nuclear forces. But the interaction can’t be explained by any of these forces.

So is there a new force out there that would upend the Standard Model? Or perhaps there’s some undiscovered particle that’s causing the difference. It could be a while before we see fully-developed new versions of the Standard Model. But there are already proposed names for a fifth force. My favourite suggestion so far is ‘flavour’.

This cartoon explains it well.

Curious: Chechnya leader’s two wives?

Has Ramzan Kadyrov, the leader of Chechnya, secretly taken a beauty queen as a second wife? The Organized Crime and Corruption Reporting Project claims that Kadyrov is married to Fatima Khazuyeva, who he first met at a beauty pageant when she was just 14.

While it’s unclear how long ago they married, the Project reports that she is now a millionaire, partly due to grants from Russian government charities.

Bigamy is illegal in Chechnya, but it’s legal under some forms of Islamic law and is widely practiced there.

There’s even a rumour that Kadyrov might secretly have a third wife!

Coming soon for subscribers: Labour Leader Keir Starmer first year

Keir Starmer became leader of the UK Labour party a year ago. The article will look at Starmer’s first year and think about the challenges he’s facing if he wants to take on Boris Johnson and lead Labour back into power. Coming soon.

Thanks for reading!