Why would you boost your immunity to a strain that is no longer in circulation i.e. Wuhan ? I don’t understand how a booster can offer protection when many mutations have occurred.
Would you take a two year old flu jab? Personally I would not. Neither would it be offered to me as they are updated annually to match the top 3 or 4 variants in circulation. Otherwise they don’t give protection. Occasionally they don’t get the cocktail correct. A few years back I got Aussie flu as it wasn’t included in the jab.
It's not the same situation.
The covid vaccines also worked very effectively against Alpha and Delta variants in terms of protection against infection.
The booster boosts your immunity against coronavirus strains including Omicron. It triggers neutralizing antibodies against Omicron, though fewer than it triggered for other variants. Omicron has more mutations than the other strains but not so many that if vaccinated your immune system doesn't recognise it as covid.
And these antibodies wane.
Importantly against all strains it provides durable protection against severe covid - through your immune system T cells.
This protection wanes more slowly and the seems to wane faster in older people.
So that's why a booster of the same vaccine for covid can still be beneficial - more so for those who need the boost or if you are dealing with vulnerable people, then when boosted you are less likely to get infected.
A study of triple vaccinated people in Qatar versus Omicron showed a 52% reduction in cases, although this wanes after 4 months.
Whereas if you get an influenza A strain in the flu vaccine that is a mis-match to the strains, there doesn't appear to be any immune benefit.
There are some indications that influenza B protection is more widespread \ less specific - it hits children hardest. So a 2 year old flu jab with influenza B in it would still be beneficial.
With Omicron subvariant BA.5 on the rise, many Americans are debating how best to protect themselves. Here's what experts say.
fortune.com
Studies found that COVID-19 vaccines elicit T cells that recognize the Omicron variant despite the many mutations in its spike protein.
The vaccines were designed to teach the immune system to recognize a key part of the spike protein. But they were developed using the initial SARS-CoV-2 spike protein. Studies have found that antibodies generated by these vaccines don’t recognize their targets as well in heavily mutated variants like Omicron.
They observed substantially fewer memory B cells and neutralizing antibodies in the blood of people 6 months after vaccination. Memory B cells help to quickly produce antibodies against previously encountered viruses or other pathogens. Having fewer neutralizing antibodies increases the risk of “breakthrough” infections—when vaccinated people are reinfected.
In contrast to antibodies, the team found that T cell responses from the vaccines recognized all variants, including Delta and Omicron. The majority of T cell responses remained effective against Omicron. Six months after vaccination, 84% of CD4+ (helper) T cell responses and 85% of CD8+ (killer) T cell responses against Omicron remained the same compared to early variants...
Despite reduced antibody responses against the variants, T cells serve as a second line of defense. This may help to explain why Omicron infections, while easily spread, are less likely to lead to severe disease in fully vaccinated people.
Studies found that COVID-19 vaccines elicit T cells that recognize the Omicron variant despite the many mutations in its spike protein.
www.nih.gov