A closer look at the study on covid risks due to variants after a single vaccine dose

The published report

The published report

The report that people with only one dose of the vaccine remain vulnerable to variants has weighed on risk assets today.

Here’s the abstract:

SARS-CoV-2 vaccine rollout has coincided with the spread of variants of concern. We investigated if single dose vaccination, with or without prior infection, confers cross protective immunity to variants. We analyzed T and B cell responses after first dose vaccination with the Pfizer/BioNTech mRNA vaccine BNT162b2 in healthcare workers (HCW) followed longitudinally, with or without prior Wuhan-Hu-1 SARS-CoV-2 infection. After one dose, individuals with prior infection showed enhanced T cell immunity, antibody secreting memory B cell response to spike and neutralizing antibodies effective against B.1.1.7 and B.1.351. By comparison, HCW receiving one vaccine dose without prior infection showed reduced immunity against variants. B.1.1.7 and B.1.351 spike mutations resulted in increased, abrogated or unchanged T cell responses depending on human leukocyte antigen (HLA) polymorphisms. Single dose vaccination with BNT162b2 in the context of prior infection with a heterologous variant substantially enhances neutralizing antibody responses against variants.

So what they’re really comparing here is 1) people who have had one dose and previously contracted covid-19 vs 2) people who have just had one dose.

It’s no surprise that people who have fought off the virus have more protection.

All this says is that people with only one dose and no prior covid have “reduced immunity against variants.”

For markets (and public health officials) a key question is whether that one dose is enough to keep the vast majority of people out of hospital. 

The study says this:

Ninety six percent (22/23) of vaccinated post infection individuals made a T cell response to spike protein compared to 70% (16/23) of vaccinated naïve individuals, with a 4-fold increase in magnitude of T cell response.

The study does hint that people with only one dose fall below the ‘protective threshold’ but it’s not clear if that just means a light infection or something worrisome but this isn’t comforting:

This finding indicates potentially poor protection against B.1.1.7 and B.1.351 in individuals who have experienced natural infection or who have only had one vaccine dose.

I suspect we’ll be hearing more about this.

The second question is: How much will it matter to markets?

The theme of the past 8-10 months has been looking beyond the virus so a modest setback in timing (3-4 months?) shouldn’t be that big of a deal. Oil might be vulnerable on the timing mismatch so that’s one to watch and this could mean even more government spending (bond negative) so that’s something to think about.

For me, though, I’m more worried about vaccine hesitancy than this.

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