Thread by @celinegounder

1/ New @NEJM study from Israel on immunity from Pfizer vaccine out to 6+ months.
nejm.org/doi/full/10.10…

Study participants were healthcare workers at a big hospital.

They provided blood samples before getting vaccinated & then monthly x 6 months.

None had COVID prior to vaxx.

2/ Antibody responses were measured for 6 months after 2nd dose of the Pfizer vaccine.

Antibody titers were highest days 4-30 after 2nd dose.

Antibody titers dropped over time.

THIS IS TO BE EXPECTED.

https://twitter.com/celinegounder/status/1417549373987344391?s=20

3/ Not surprisingly, antibody titers started lower and dropped down lower among older persons (65+) than younger persons (<45).

4/ Antibody titers, especially neutralizing antibody titers, started lower and dropped down lower among men than women.

5/ At 6 months after 2nd dose of Pfizer vaccine, antibody titers were significantly LOWER among:
- 65+ year-olds
- males
- persons with 2+ chronic medical conditions (e.g. hypertension, diabetes, ⬆️cholesterol,
❤️/🫁/kidney/liver disease)
- autoimmune disease
- immunocompromise

6/ At 6 months after 2nd dose of Pfizer vaccine, antibody titers were significantly HIGHER among:
- persons with obesity (BMI 30+) -- huh?

7/ Antibody titers DOES NOT EQUAL neutralizing antibody titers.

Persons with 2+ chronic medical conditions did NOT have lower neutralizing antibody titers at 6 months after 2nd dose of Pfizer.

Ditto for persons with autoimmune disease.

8/ Immunocompromised persons had lower antibody and neutralizing antibody titers.

Obese patients (BMI 30+) had higher neutralizing antibody titers than non-obese patients.

9/ Decay in NEUTRALIZING antibody titers was correlated with initial levels:
- high initial levels correlated with faster decay out to ~2 months after 2nd dose

10/ There was a correlation between antibody titers and neutralizing antibody titers, but that correlation wasn't perfect and varied over time.

11/ It might seem weird that obese persons had higher neutralizing antibody levels given that obese patients are at higher risk for severe COVID.

12/ But higher antibody responses are also associated with severe COVID (a hyperinflammatory, dysfunctional immune response).

It's unclear if higher neutralizing antibody levels in obese persons translates into better or lesser protection.

13/ Antibody titers and neutralizing antibody titers decay less rapidly among people who had natural infection vs vaccination.

But note that the immune response among naturally infected people is also less predictable/reliable.

14/ Vaccination + Infection = Hybrid immunity
science.org/doi/10.1126/sc…

Hybrid immunity may be the most long-lived and robust of all.

15/ Also on this paper:

https://twitter.com/deeptabhattacha/status/1446119109448454160?s=20