What does it mean that a Covid vaccine is, say, 70% effective?

Let’s start by talking about what it doesn’t mean. If a vaccine is 70% effective against a virus it doesn’t mean that 30% of the people who’ve been vaccinated will get infected. That’s an assumption that only people whose math is as bad as mine would make. The kind of people who juggle the numbers 70, 30, and 100 and come up with an answer that’s as likely looking as it is meaningless.

It turns out that the number doesn’t compare the vaccinated people who stay well to the  vaccinated people who get sick. Nay, verily, it compares the vaccinated people who get sick (or who stay well) to the unvaccinated people who get sick (or who stay well). To put that a different way (because I don’t know about you, but I’m struggling with this), it compares the risk vaccinated people run in the presence of Covid to the risk unvaccinated people run.

This matters because it leaves us with a much smaller pool of people who are vulnerable.

If you’d care to read about that with actual numbers and sensible writers, follow the link. I have a severe allergy to math and I know better than to attempt a full explanation. 

Irrelevant photo: Red clover. I’ll come back with more kitten photos soon.

 

Who gets sick with the Delta variant and can the vaccinated spread it?

In the US, 95% to 98% of the people hospitalized with Covid are unvaccinated, and 99.5% of the deaths are of the unvaccinated. Even with the Delta variant circulating, that seems to be holding true.

But some numbers have changed since the initial vaccine studies, and they have to do with what Dr. Robert Schooley, from the Department of Medicine at UC San Diego’s School of Medicine, calls “the asymptomatic shedding rate among vaccinated individuals,” which in human speech means how much of the virus is spread by vaccinated people who get infected but don’t get sick.

Or to push that one step further, how dangerous they are to the unvaccinated.

When the vaccines were tested, the Delta variant wasn’t around yet. They were dealing with a less infectious beast. On top of which, no one thought to investigate the odd sniffles and colds that people in the study cooked up. They were allergies. They were colds. They were flu. 

Remember the old days, when people caught colds? 

So the study didn’t track them.

Now, though, they’re realizing that those mild symptoms could be nearly asymptomatic Covid, and what’s known so far is that some fully vaccinated people who get infected carry enough of the virus to spread it, even though it’s not making them sick.

How do they compare with unvaccinated people as far as spreading the thing goes? The numbers aren’t in yet. I mean, they’re out there. Numbers always are. But nobody’s assembled them yet. On average, though, Schooley says the infected vaccinated person will shed less virus for a shorter time. And the odds that they’ll become infected are lower, so whatever the eventual picture turns out to be, vaccinating people does slow the spread of the disease.

 

Are the vaccines losing their effectiveness? 

As has become usual since the pandemic started, we’re not likely to find a definitive answer yet, but it does look like the number of breakthrough cases in vaccinated people is growing.

What’s a breakthrough case? A Covid case in someone who’s vaccinated. Getting one doesn’t mean you’re dead, hospitalized, or even necessarily sick. It just means you’re carrying the infection, when if the vaccines were 100% effective (very few are and no one expected these to be), you wouldn’t be. 

So if you’re fully vaccinated, it’s not time to panic yet. You can always do that later. 

Why’s this happening? The experts are still debating that, but it doesn’t look like the Delta variant is evading either the vaccines or immunity from earlier infections. 

That’s another reason to wait before you panic.

If Delta hasn’t broken through the vaccines’ protective lines, that leaves us with two possibilities. One, the vaccines’ effectiveness is fading, or two, Delta’s high transmissibility is responsible.

Several studies show what could be a waning in vaccine effectiveness, but it’s hard to know if the numbers really mean that. They could also mean that vaccinated people are taking more risks–going to bars or gyms or other Covid exchange sites–and giving themselves more chances to meet the virus.

And protection against getting so sick that you need to be hospitalized, though, is holding steady, which may mean effectiveness isn’t waning. All this will be perfectly clear in hindsight, but for now we have to make do with what we can see from where we are.

So do booster shots make sense? 

On the side of saying no are the many countries that the vaccines have barely reached. How can rich countries be talking about booster shots when initial doses are desperately needed elsewhere?

On the side of saying yes is that in people with weakened immune systems, because of either age or disease, they can make a difference, although the evidence on that is still preliminary.

 

Testing news

A new study shows that testing saliva for Covid is as reliable as testing nasal swabs. So at some point we may be able to stop puncturing our brain pans with sticks that are allegedly softened with cotton wool–or something that looks vaguely like cotton wool.

If Covid tests shift to using saliva, they won’t have to rely on patents’ willingness to make themselves uncomfortable, which will make them more reliable. And we won’t have to worry about a shortage of swabs.

If, in fact, worrying about that is one of the things that’s keeping you up at night.

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Several times now, I’ve sworn off writing about newer, faster, cheaper Covid tests because although I keep reading about them, they never seem to be adopted–at least not anywhere I read about, and certainly not where I live. But you know how it is when you swear off something multiple times: It’s a sign that you keep breaking your word. So here we go again:

A newer, faster, cheaper Covid test has been developed. And it uses the same stuff that pencil lead is made from, which isn’t lead at all, it’s graphite. It cuts the cost to $1.50 per test, takes six and a half minutes, and is 100% accurate using a saliva sample and 88% using one of those evil nasal thingies.

The system can be adapted to test for other transmissible diseases. Now all we have to do is wait and see whether we hear of it again.

Real-world information on Covid vaccine effectiveness

For the first time, we have some real-world data about how effective the Covid vaccines are. The good news is that a very small percent of fully vaccinated people get sick. The bad news is that the vaccines aren’t  a three-hundred percent effective suit of armor against serious disease. Or even quite one hundred percent.

Among the 77 million fully vaccinated people in the US, the Centers for Disease Control reports 5,800 Covid cases. That’s somewhere in the neighborhood of 0.0001%. Of that group, 7% were hospitalized and 74 died, and damn it I wish they’d give statistics either entirely in percentages or entirely in absolute numbers to dopes like me could compare them. I can get as far as saying that most of the cases have been either mild or asymptomatic. If you can translate, leave me a comment. Even if your answer’s wrong, I’m not likely to know. 

Infections in vaccinated people are called breakthrough infections, and it would be unusual if they didn’t happen. They were found in all age groups, although 40% were in people who were 60 or older, 65% were in women, and 29% were asymptomatic. 

Irrelevant photo: apple blossoms

So far, they haven’t identified what, if any, risk factors incline vaccinated people toward getting Covid or which (if any) variants are more likely to be involved, but believe me, someone’s staying up late crunching numbers. It’s also not clear how the asymptomatic cases were noticed, since it’s unusual to test fully vaccinated people who show no symptoms. It could be that they were hospitalized for other reasons and a Covid test was run as part of the admissions routine. Whatever the reasons, though, we can assume that the number of asymptomatic infections is an underestimate.

But didn’t they tell us that the vaccines were 100% effective against severe Covid? Yup, they did, and they weren’t lying to us. The odds of a fully vaccinated person getting a severe infection are so small that the sample would’ve had to be insanely large for a case to have surfaced. The people who ran the trial gave us the numbers they had. As real-world information comes in, those numbers change. That’s the annoying thing about the real world. Every so often, it doesn’t line up with our predictions.

I get a rightwing newsletter in my inbox every so often–it’s been interesting so I don’t unsubscribe, although I’m not the person they have in mind–and it’s fond of reporting on cases of people catching Covid after being vaccinated. The tone leans heavily toward See? We told you it didn’t work. If I could, I’d compare that 0.0001% of breakthrough infections with the percentage of unvaccinated people who catch Covid in the US, but we’ll need a person with some minimal mathematical competence to work it out. I asked Lord Google but he was in one of his moods. If you’d like percentages on many unrelated things, I can point you in the right direction. 

The conclusion, if you want one to put in your pocket and take it home, is that the vaccines aren’t 110% effective and we still need to be careful, but we can let go of the anxiety. The numbers are on our side here and the anxiety isn’t helping anyway.

There’s nothing like someone telling you not to be anxious to make you less anxious, is there?

The additional conclusion is, keep the mask. Even if you’re vaccinated, you can still spread the disease. You’re less likely to–if you have an asymptomatic case you’re likely to have a lower viral load–but you can still do some damage. Other people share this world with us. Try not to do them any more harm than you can help.

 

What’s the story on vaccines and blood clots?

The two vaccines that have been linked to very rare incidents of blood clots are based on a single technology–one they share with the Russian Sputnik V vaccine. Basically, they take an adenovirus–that’s a virus that causes colds–deactivate it, and turn it into a chariot for the vaccine to ride in on.

Vaccines are hopelessly vain. They can’t resist a grand entrance. Horses, polished metal catching the sun, noise, dust, cameras. 

The clotting problem seems–and we’re still at the stage of seems–to be related to that damn chariot. 

The clots happen in veins in the brain, in the abdomen, and in arteries, and at the same time the person’s level of blood platelets fall, and those platelets are the beasties that help our blood clot. We end up with blood clots happening at the same time as hemorrhages, which in everyday English means bleeding. That’s kind of like an elevator going up and down at the same time. 

Normally, you’d pour an anticoagulant called heparin into a person with a blood clot forming in scary places, but when you pair the clots with hemorrhages, you can’t do that.

What are the signs that a person’s getting a serious reaction to one of the vaccines? Severe headaches, abdominal or leg pain, or shortness of breath within three weeks after vaccination.

Every article about this says the clots are very rare. 

How rare is very rare? Last I checked, 222 cases had been linked to the AstraZeneca vaccine in Europe and Britain, along with 18 deaths. That’s out of 34 million people who’ve gotten the vaccine. Most of those were in women who were–okay, not young but under 60, which looks younger all the time. In the US, the Johnson & Johnson vaccine has been linked to 6 cases out of 6.8 million people who were vaccinated with it.

So how rare are the clotting problems? About the same as the chance of being struck by lighting in the UK in any year you choose. And that’s in a country that, by comparison with the American Midwest, doesn’t get a hell of a lot of lightning.

The risk of Covid, though, is no small thing. 

And if you’re inclined to roll the dice by going unvaccinated, the risk of having a blood clot after a bout of Covid is 8 times higher than after getting the AstraZeneca vaccine. The risk of clots after Covid is 100 times higher than after a normal infection.

 

Covid immunity and prior infections

And vaguely related to that is the news that having had Covid doesn’t give young people full protection from another bout of it. That’s from a study of 3,000 healthy U.S. Marines who were between 18 and 20 years old and unless the regulations have changed since last I looked had radically and irrelevantly short hair.

Even though the marines had antibodies, they didn’t have the level of protection that the vaccine offers: 10% got reinfected. That compares with 50% who hadn’t had an earlier infection, although in the previously infected group 84% of the infections  were asymptomatic or mild compared to 68% in the previously uninfected group.

The numbers of infections and reinfections were higher than would be likely outside of a military base because of the cramped living conditions and close contact.

The advice to people who’ve recovered from Covid is to boost your immunity with a vaccine.