Hacker News Reader

Comment by lnyan | Hacker News Reader

Discussion from this paper:

  "Although BA.2 is considered as an Omicron variant, its genomic sequence is heavily different from BA.1, which suggests that the virological characteristics of BA.2 is different from that of BA.1. Here, we elucidated the virological characteristics of BA.2, such as its higher effective reproduction number, higher fusogenicity, higher pathogenicity when compared to BA.1. Moreover, we demonstrated that BA.2 is resistant to the BA.1-induced humoral immunity. Our data indicate that BA.2 is virologically different from BA.1 and raise a proposal that BA.2 should be given a letter of the Greek alphabet and be distinguished from BA.1, a commonly recognized Omicron variant."

View on HN

It certainly sounds ominous, but the experiments were done in hamsters, whereas human exposure to BA.2 doesn’t seem to pan out the same way.

https://www.bloomberg.com/news/articles/2022-02-16/study-sho...

>Among 95,470 infections analyzed by the national laboratory, 3.6% of those with BA.2 were hospitalized, compared with 3.4% of those with the original strain [BA.1]. Among 3,058 hospitalized patients, 30.5% of those infected with BA.2 developed severe disease compared with 33.5% of those with the original omicron version.

And even if we disregard these real-world results in humans, the hamster experiment found that BA.2 was equivalent in lung pathology and overall fusogenicity to B.1.1/D614G, which is still far less fusogenic than delta. Fusogenicity is linked to lymphopenia[1] and blood clots/stroke[2].

1. https://www.nature.com/articles/s41418-021-00795-y

2. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8664391/

They did test against antibodies from human sera samples (Figure 2E), but as parent commenter noted, this doesn't test for T-cell mediated responses.

As we’ve seen time and time again it’s T-cells that actually matter.

Does it really matter that it's resistant to BA.1 induced humoral immunity?

From the BA.1 variant we learned that cell mediated immunity is more important to end the pandemic.

The media got very loud that the 4th vaccine doesn't help to stop people from getting sick, but it required a month more data to see that it is worth to be injected to decrease the probability of serious illness / death.

Yeah, its not clear if preventing symptomatic infection is as crucial an end-point in contrast to preventing hospitalization, the latter of which is indeed mediated by T-cell immunity rather than antibody titers. The following detail is worth noting though ---

"Vaccine sera were collected from sixteen vaccinees four weeks after the second vaccination with mRNA-1273 (Moderna)"

So it seems like they haven't tested against sera from people who got three doses? Response to BA.1 was better with three doses than two, but I think if the data from Israel was to go by, the impact of the third dose on antibody titers also waned over time (although T-cell mediated immunity stayed the same in terms of % hospitalized).

> Response to BA.1 was better with three doses than two

Not under 60, though.

Source?

Reply on news.ycombinator.com