Stats Chat

Team Ratings for Round 13

The basic method is described on my Department home page.
Here are the team ratings prior to this week’s games, along with the ratings at the start of the season.

Performance So Far

So far there have been 38 matches played, 21 of which were correctly predicted, a success rate of 55.3%.
Here are the predictions for last week’s games.

Predictions for Round 13

Here are the predictions for Round 13. The prediction is my estimated expected points difference with a positive margin being a win to the home team, and a negative margin a win to the away team.

The external scientific advisory committee for the FDA meets next week to consider the Pfizer Covid vaccine in kids 5-12.  Pfizer’s briefing to the committee is now up on the website; the FDA briefing is not (as of midday Saturday).

Demographically, the trial isn’t as representative as the initial adult trials, which were much better than usual. About 10% of the participants had asthma and about 10% were obese. Black and Hispanic populations were under-represented by about a half relative to the US population —  though there has been no indication that race/ethnicity matters for vaccine efficacy so far.

For the extension to ages 5-12 there are basically three questions

1. Is the dose right? They used 1/3 of the adult dose. Using too much would increase  adverse effects; using too little would not provide reliable immunity
2. Is there anything new and worrying about adverse effects? This trial, like all randomised trials, is too small to see surprising and rare adverse reactions that happen to 1 person in 10,000 or 1 in a million. These can only ever be picked up by post-marketing surveillance, as we’ve seen for both the Pfizer and AstraZeneca vaccines. Safety signals in the trial would involve milder, less rare reactions at elevated rates.
3. What is the risk/benefit relationship like, given the relatively lower risk from Covid in kids and the fact that (in contrast to many infectious diseases) kids don’t seem to spread it more effectively than adults do?

The data are positive on the first point. Pain and redness at the injection site are a bit more common than with teenagers given the full dose; systemic reactions such as fatigue and fever are a bit less common.  Levels of neutralising antibodies are about the same as in teenagers given the full dose.

On the second point, the trial is again positive. Nothing new seems to have been seen (though this is where the FDA briefing will be important, to see if they agree — how you classify adverse events can make a difference).

It’s harder to say what regulators will think for the third point, but if the FDA were willing in principle to approve based on a trial of this general design there doesn’t seem to be anything obvious in the results that would make them not approve based on these data.

Update: FDA’s briefing is now available.  The main new information is an explicit risk-benefit analysis. As you’d expect, the net benefit depends on the Covid incidence, but they say the net benefit might be positive even under the lowest-incidence case (and that’s assuming only 80% effectiveness against hospitalisation, which is probably a bit low, and a pessimistic view of the data on myocarditis). They don’t seem to model any community effect of vaccination by reducing infection in other people and thus reducing exposure to the virus. Risk-benefit is where the most interesting discussion should be at next week’s meeting.

Team Ratings for Week 5

The basic method is described on my Department home page.
Here are the team ratings prior to this week’s games, along with the ratings at the start of the season.

Performance So Far

So far there have been 32 matches played, 25 of which were correctly predicted, a success rate of 78.1%.
Here are the predictions for last week’s games.

Predictions for Week 5

Here are the predictions for Week 5. The prediction is my estimated expected points difference with a positive margin being a win to the home team, and a negative margin a win to the away team.

Team Ratings for Round 8

The basic method is described on my Department home page.
Here are the team ratings prior to this week’s games, along with the ratings at the start of the season.

Performance So Far

So far there have been 49 matches played, 37 of which were correctly predicted, a success rate of 75.5%.
Here are the predictions for last week’s games.

Predictions for Round 8

Here are the predictions for Round 8. The prediction is my estimated expected points difference with a positive margin being a win to the home team, and a negative margin a win to the away team.

Team Ratings for Round 6

The basic method is described on my Department home page.
Here are the team ratings prior to this week’s games, along with the ratings at the start of the season.

Performance So Far

So far there have been 30 matches played, 14 of which were correctly predicted, a success rate of 46.7%.
Here are the predictions for last week’s games.

Predictions for Round 6

Here are the predictions for Round 6. The prediction is my estimated expected points difference with a positive margin being a win to the home team, and a negative margin a win to the away team.

Team Ratings for Round 12

The basic method is described on my Department home page.
Here are the team ratings prior to this week’s games, along with the ratings at the start of the season.

Performance So Far

So far there have been 35 matches played, 19 of which were correctly predicted, a success rate of 54.3%.
Here are the predictions for last week’s games.

Predictions for Round 12

Here are the predictions for Round 12. The prediction is my estimated expected points difference with a positive margin being a win to the home team, and a negative margin a win to the away team.

It’s time for NZ’s Bird of the Year.  There are two important things to remember about Bird of the Year. First, if you’re going to talk about it on social media use the appropriate hashtag so normal people can mute you.  Second, Bird of the Year is a popularity contest driven by who votes and by last minute social influences; it doesn’t tell us anything new about the birds themselves or really even anything about their popularity in other settings. That’s not the thing you need to remember. The thing you need to remember is that all other online bogus clicky polls work the same way.

I’m campaigning for kākāpō because Zoe Luo, who is doing a PhD with me, is working on ways to model the genetics of rare species, using kākāpō as an example.  The entire kākāpō species had full genome sequencing done.  You usually can’t do that; Zoe is looking at how to use genome sequencing on a sample of the population together with other information on the rest of the birds to fit similar statistical models to the ones you would fit with full genome sequencing.  We can do this with the kākāpō because it’s easy to see what how well your models would work if you had less data than you really do — you can just ignore some of it — but it’s harder to see how well your models would work if you had more data than you really do.

Today is the NZ Vaxathon! I had my second dose last week. All the statisticians I’ve talked to on the issue have had either one or two doses depending on when they became eligible.  For fans of anecdata, our experience varied from no adverse effects at all to a day or so feeling pretty bloody average, consistent with what the randomised trial reported.

In the spirit of StatsChat, here are some links to primary sources for anyone who wants to do their own reading rather than getting clinicians and scientists to translate it

• Official guidance from the US Food and Drug Administration on what sort of evidence they would need to approve a Covid vaccine (June 2020)
• The protocol (plan) for the Pfizer vaccine trial. It’s unusual for these to be public, but it was reassuring when this one was published last year (PDF)
• The meeting briefings for the external expert advisory committee meeting that recommended authorisation of the vaccine. You want ‘Briefing Document -FDA’ and ‘Briefing Document -Sponsor’. And if you’re really dedicated, the transcript of the discussion.  This is where you get all the detailed information that doesn’t fit into a published research paper, plus discussion from the medical and scientific experts
• Real-world effectiveness assessment of the vaccine in Israel. Authors include Miguel Hernán, who is a leading expert on causal inference from observational data
• What we know about heart inflammation after vaccination: an adverse reaction in about one person per 100,000 aged under 40.  Most recover fully, but there has been one death in New Zealand that was probably due to this.
• A summary on vaccine effectiveness with links to primary sources, covering effectiveness against Delta, prevention of infection, and prevention of symptomatic disease
• Vaccination of health care workers in the UK reduced infection rates for their household members
• A recent study in China (with different vaccines) found vaccinated people were less likely to pass on the virus even with Delta
• An even more recent UK study looking at the Pfizer and AZ vaccines found the same

Team Ratings for Week 4

The basic method is described on my Department home page.
Here are the team ratings prior to this week’s games, along with the ratings at the start of the season.

Performance So Far

So far there have been 24 matches played, 19 of which were correctly predicted, a success rate of 79.2%.
Here are the predictions for last week’s games.

Predictions for Week 4

Here are the predictions for Week 4. The prediction is my estimated expected points difference with a positive margin being a win to the home team, and a negative margin a win to the away team.

Team Ratings for Round 7

The basic method is described on my Department home page.
Here are the team ratings prior to this week’s games, along with the ratings at the start of the season.

Performance So Far

So far there have been 42 matches played, 33 of which were correctly predicted, a success rate of 78.6%.
Here are the predictions for last week’s games.

Predictions for Round 7

Here are the predictions for Round 7. The prediction is my estimated expected points difference with a positive margin being a win to the home team, and a negative margin a win to the away team.