Thread by @_johnbye

PHE's study on vaccine effectiveness against the Indian B.1.617.2 variant is out, clarifying figures leaked to the FT yesterday.

It confirms the 1st dose is less effective against B.1.617.2, but the 2nd dose still gives similar protection. However...

gov.uk/government/new…

As @fascinatorfun pointed out, the FT figures mixed data from both Pfizer and AstraZeneca jabs.

The study breaks it down by vaccine and, on the face of it, isn't good news for AstraZeneca (ChAdOx1).

But they do say this may be partly due to 2nd jabs starting later for AZ.

Data for both vaccines on preventing symptomatic cases is similar 21+ days after the first dose -

Pfizer:
49% protection vs B.1.1.7
33% protection vs B.1.617.2

AstraZeneca:
51% protection vs B.1.1.7
33% protection vs B.1.617.2

So about a third less effective against B.1.617.2

Data for 14+ days after the second dose is more varied -

Pfizer:
93% protection vs B.1.1.7
88% protection vs B.1.617.2

AstraZeneca:
66% protection vs B.1.1.7
60% protection vs B.1.617.2

Only a small drop in effectiveness against B.1.617.2, but big difference between vaccines.

However, it may take more than 2 weeks after the second dose for the AstraZeneca vaccine to reach peak effectiveness.

Because its roll out started 4 weeks later, more people in the study had only got their second AZ jab in the last few weeks.

So numbers *may* improve with time.

The concern is:

- 30% of adults (and almost all children) haven't been vaccinated at all
- 30% have had one dose, which only gives 33% protection against B.1.617.2
- 40% have had two doses, but 10% were in the last 2 weeks

So lots of people still vulnerable to infection.

The good news is both vaccines are more effective at preventing serious illness and death than they are at stopping you from catching the virus at all or developing (mild) symptoms, even after only one dose.

There's no data on this for B.1.617.2 yet.

So it looks like:

- Both vaccines are less effective against B.1.617.2 after one dose
- The difference is far smaller after two doses
- Most people haven't had two doses yet though
- But even one dose should give fairly good protection against death or hospitalisation

The government press release (which today's newspaper headlines were based on) is here:
gov.uk/government/new…

The full report can be downloaded here:
khub.net/documents/1359…