Antibody levels highly predictive of immune protection from symptomatic Covid

He'll have a test against the viruses themselves next week, but he'll need to wait 2 weeks for the result for that test.

> The estimated neutralization level for protection from severe infection is approximately sixfold lower than the level required to protect from any symptomatic infection. Thus, a higher level of protection against severe infection is expected for any given level of vaccine efficacy against mild SARS-CoV-2 infection. Assuming that this relationship remains constant over time, it appears probable that immunity to severe infection may be much more durable than overall immunity to any infection. Long-term studies of antibody responses to vaccinia, measles, mumps or rubella suggest that these responses generally stabilize with half-lives of >10 years. We therefore projected beyond the reported decay of SARS-CoV-2 responses (out to 8 months after infection5), assuming that after 8 months following the infection the decay rate will slow down. We modeled the decay rate of the neutralization titer, assuming that it slowed linearly to a 10-year half-life over 1, 1.5 or 2 years (details in Methods). This analysis predicts that even without immune boosting, a significant proportion of individuals may maintain long-term protection from severe infection by an antigenically similar strain, even though they may become susceptible to mild infection (Fig. 3b,c).

Sounds like good news. This study appears to be saying that the vaccines do a 6x better job of preventing severe covid infection than the known 94% efficacy preventing even mild symptoms from appearing, and that long term immunity [0] might be expected to last decades, similar to other vaccines.

[0], EDIT: "long term protection against severe sickness", as opposed to "immunity", as pointed out by PeterHolzwarth in comment below

https://www.sciencedaily.com/releases/2021/05/210517105727.h...

Here, one of the people associated with the paper mentions:

"Vaccination works very well to prevent both symptoms and severe disease in the short to medium term, but efficacy is predicted to decline over the first few months for most of these vaccines,"

"However, it is very important to understand the difference between immunity against infection and protection from developing severe disease. Our study found that a 6-fold lower level of antibodies is required to protect against severe disease. So even though our analysis predicts that we will start losing immunity to mild infection in the first year after vaccination, protection from severe infection should be longer lived," says Dr Khoury.

Key is that distinction between immunity and protection against severe sickness.