COVID19 mini-update, July 25, 2021: waning protection against infection — but largely conserved against severe disease

Dr. John Campbell reports that in Israel, protection by the Pfizer vaccine against asymptomatic or mildly symptomatic infection is now down to just 40% (down from 90%), although protection against severe illness and hospitalization are still at 88% and 91.4%, respectively. Meanwhile, in the UK, they see still 88% protection against symptomatic infection and 96% against hospitalization. The discrepancy for the hospitalization is within overlapping uncertainties, but that for mild infections cannot be easily explained away. So what gives? And why is protection waning for mild infection but not (significantly) for severe disease? Summarizing what he’s presenting in the video in table form:

month of 2021 vaccinatedInfectionSymptomatic DiseaseHospitalizationSevere disease
March 67%69%89%94%

There are two major differences between the UK and Israel, of course. For one, the UK started out later with Pfizer so on average there was less time to wane. But in addition, the UK uses a much longer waiting period (2 months or more) between the first and second jabs than the 3 weeks applied by Israel and the USA. There is clear evidence that the longer the waiting period between jabs, the better the protection.

That still leaves the question of why the protection against severe disease is so much better conserved. I talked to an immunologist at [name of research hospital redacted]. She told me the following (trying to summarize from memory):

  • we should understand that COVID is a disease with multiple stages. The upper respiratory stage is a nuisance but not in itself dangerous; if it “travels down” to the lower lung, however, you are in deep trouble. These “travels” however on average will take 3 days or more — enough for a ‘primed’ immune system to mount an effective immune response.
  • antibody levels do drop pretty quickly, although with considerable variation between vaccinated (or recovered) persons: some have plenty of antibodies after 6 months, others lose them all, yet others are borderline.
  • antibody titers are however only half the immune story: what matters for long-term immunity are “memory cells”
  • unfortunately for research purposes, while antibody levels can be quickly and easily assessed by an ELISA test, not too many people are keen on having biopsies taken from bone marrow and the spleen, so you are reduced to trying to catch a few such cells as they travel around in the bloodstream. “This is so expensive and tricky, regardless of whether it’s COVID or something else, that doing this on even 50 people is only worth it for a paper in a high-profile journal”.
  • the upper respiratory tract isn’t the easiest place to generate lots of antibodies at the best of times. Maybe if a reliable intranasal droplet vaccine could be developed?
  • That said, as long as memory cells can mount a good immune response in less than 3 days, your COVID infection doesn’t proceed to the more dangerous stage and yihye be-seder (it will be OK).

To use a military metaphor: the antibodies are like guardians on the ramparts, while the “memory cells” allow quickly mounting and sending out a rapid response force.

In another video, Dr. Campbell presents recent research that seems to indicate much higher viral loads (about 3 orders of magnitude) higher than for the “wild type” (a.k.a. Classic Covid).

Interesting developing story — stay tuned.

UPDATE: more here:

FINALLY, a separate Oxford University study that was published over the weekend found that an eight-week gap between the first and second doses of the Pfizer vaccine is a “sweet spot” when it comes to generating neutralizing antibodies.When England launched its vaccination campaign, it did not have enough doses to vaccinate the population according to Pfizer’s recommended regime of two doses three weeks apart. As such, it spread doses out to between four and 12 weeks to allow more people to get at least one jab.Specifically, the new research showed that neutralizing antibody levels, the level of those antibodies responsible for defending cells from pathogens, were higher after the extended dosing interval (six to 14 weeks) compared to the conventional three-to-four-week regime.


[Another difference] is age.Both Israel and the UK were careful to first vaccinate healthcare workers and the elderly. In England, however, the older population was largely administered the AstraZeneca vaccine, whereas people under 40 were offered Pfizer or Moderna as an alternative, due to evidence linking AstraZeneca to rare blood clots. The same study showed that the AstraZeneca vaccine was only 67% effective against symptomatic disease after two doses.In Israel, everyone received Pfizer. Breakthrough infections were most prominent among people aged 60 and older, a cohort that already has a greater tendency to be immunocompromised

7 thoughts on “COVID19 mini-update, July 25, 2021: waning protection against infection — but largely conserved against severe disease

  1. It looks like the UK results are pfizer only. The UK should of course be able to produce comparison between pfizer, AZ (and Moderna?) as well. Those are going to be really interesting when they come out (if they haven’t done so).

    • It was an attempt to make sense of the discrepancy between UK and Israeli findings. It appears that Oxford/AstraZeneca doesn’t lose much of its (lower to begin with, to be sure) effectiveness over the time interval surveyed — but again, they used a long interval between shots (a result of their decision to get as many people as possible first shots before rolling out seconds — the said decision may have been serendipitous)

  2. Is it true that the Covid diag test can’t distinguish between Covid and normal flu? Distracting amounts of conflicting info now.

    I’m seeing reports that travel to Israel from US is discouraged. Israel bumped to “Reconsider Travel”

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