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Birmingham, 18 February (Dialogue) After a COVID infection, whether it’s the first, second or third time, many of us wonder how long we can stay safe from reinfection, and how we Is it vulnerable to new variants. Also, if we get COVID again, does the immunity we gain from this infection make the next infection less severe?
A new study published in The Lancet set out to answer these questions, examining the strength and duration of natural immunity in COVID variants.
The authors collected data from 65 studies in 19 countries, making it the largest review on the topic to date. These studies compared the risk of COVID in people who were previously infected with those who were not. Studies combining natural immunity with vaccination (mixed immunity) were excluded.
The researchers aimed to assess whether infection conferred similar protection against reinfection with the different variants, and whether this protection varied over time.
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These analyzes cover studies from the onset of the pandemic to September 2022 and focus on alpha, beta, delta and omicron BA.1 variants.
prevent reinfection
The authors assessed protection against reinfection, symptomatic disease, and severe disease (defined as hospitalization or death) separately.
They found that previous infection was highly protective against reinfection with alpha, beta and delta variants, but less so with omicron BA.1. Previous infection conferred modest protection against reinfection with omicron BA.1 compared with reinfection with omicron BA.1 (45%), and greater protection against reinfection with omicron BA.1 (82%). The same goes for symptomatic infection.
Data from the long-term study showed that, within 40 weeks, the reinfection protection rate of the pre-omicron variant dropped to 78.6%, while that of the omicron BA.1 dropped even faster, to 36.1%.
However, when assessed for severe disease, all variants showed a sustained protection rate of greater than 88% through 40 weeks. That’s not to say that protection drops off significantly after 40 weeks. Instead, there appears to be only limited available data that followed people long enough for the authors to draw strong conclusions beyond that time frame.
The results also showed that for the pre-omicron and omicron BA.1 variants, protection against severe disease following natural infection was comparable to that of two vaccine doses.
understand the findings
Years is a long time for a highly contagious respiratory virus, and SARS-CoV-2 (the virus that causes COVID) is no exception. Compared with the ancestral virus, it has produced a worrying continuous variant with a higher ability to transmit and evade our immune response.
When we consider how the omicron variant differs from its predecessor, the observations of this study are protected against the former omicron variant and omicron BA.1, respectively.
As background, neutralizing antibodies produced after previous viral infection are important to prevent subsequent viral entry into susceptible cells. These Y-shaped molecules recognize intact proteins on the outside of the virus and attach to them, preventing the virus from locking onto the cellular receptors needed for infection.
But to persist, viruses like SARS-CoV-2 introduce random mutations into their genomes as they replicate, designed to continually alter their proteins to evade immune recognition.
Omicron lineages have enough mutations to be significantly different from previous variants and thus evade existing antibodies. Evasion of neutralizing antibodies explains our failure to control reinfection with omicron variants.
Thankfully, we don’t just rely on antibodies for protection. A type of immune cell called a T cell recognizes viral protein fragments rather than the complete protein. This means that more mutations are required in the viral genome to fully evade T cell immunity.
Unlike antibodies, T cells do not look for viruses. Instead, they recognize infected cells and eliminate them quickly to reduce the body’s viral factories. Thus, T cells act where neutralizing antibodies may fail after infection. A robust T-cell response to the coronavirus is crucial to preventing severe disease, and fortunately, omicrons are much harder to escape.
SARS-CoV-2-specific T cells decay more slowly than antibodies. In fact, people who were infected with a SARS-like coronavirus in 2003 still had T cells that recognized SARS-CoV-2 17 years after infection.
Infections and Vaccinations
While natural infection may offer protection equivalent to vaccination, that doesn’t mean you should seek to become infected. SARS-CoV-2 remains a dangerous and unpredictable virus, in some cases causing a series of devastating effects that persist long after recovery.
The authors suggest that a person’s prior infection status and timing should be considered along with booster vaccination to predict protection. However, this may be difficult to implement because infection surveillance has been reduced in most countries compared to the early days of the pandemic. Anyway, COVID certificates are less commonly used these days.
They also suggest that their findings could be used to inform the best time to step up vaccination strategies. That said, it may be beneficial to wait a while after infection before getting a booster shot.
Further high-quality, long-term follow-up studies will be important to complement these findings, as the authors acknowledge that there are not many studies on natural infection compared to protection following vaccination. There are also few studies mapping conservation against newer omicron sublineages. As the pandemic continues, much remains to be learned about immune protection against this evolving virus. (dialogue)
(This is an unedited and auto-generated story from a Syndicated News feed, the content body may not have been modified or edited by LatestLY staff)
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