Getting the COVID and flu shot together?
A new Italian study in Cytokine found that the early inflammatory response after getting COVID-19 and flu vaccines at the same time may actually limit how long your antibody protection lasts🧵
A new Italian study in Cytokine found that the early inflammatory response after getting COVID-19 and flu vaccines at the same time may actually limit how long your antibody protection lasts🧵
https://twitter.com/harryspoelstra/status/1986725315356352755
29 healthcare workers received both
an mRNA COVID-19 (XBB.1.5) booster
a quadrivalent inactivated flu shot.
Blood was collected
before vaccination (T0)
5 days later (T1)
after 3 months (T2)
after 6 months (T3)
an mRNA COVID-19 (XBB.1.5) booster
a quadrivalent inactivated flu shot.
Blood was collected
before vaccination (T0)
5 days later (T1)
after 3 months (T2)
after 6 months (T3)
Within just 5 days, levels of inflammatory cytokines shot up -
especially IL-6, CXCL10, and TNF-α.
In some people, IL-8 also spiked and strongly correlated with IL-6.
That means their innate immune system went into high gear.
especially IL-6, CXCL10, and TNF-α.
In some people, IL-8 also spiked and strongly correlated with IL-6.
That means their innate immune system went into high gear.
When scientists checked antibody levels later on, they found
The higher your IL-6 and IL-8 response at day 5,
the lower your anti-spike IgG at 3 and 6 months.
So - a stronger early inflammation = faster antibody decline.
The higher your IL-6 and IL-8 response at day 5,
the lower your anti-spike IgG at 3 and 6 months.
So - a stronger early inflammation = faster antibody decline.
This wasn’t an all-or-nothing pattern - it was continuous.
Everyone responded, but those with the highest IL-6/IL-8 bursts lost antibodies more quickly.
It’s a dose-response relationship, not a random fluke.
Everyone responded, but those with the highest IL-6/IL-8 bursts lost antibodies more quickly.
It’s a dose-response relationship, not a random fluke.
Why does this matter?
IL-6 and IL-8 drive short-term inflammation.
If they rise too much, they can disrupt germinal center formation -
where long-lived memory B cells are made.
You get quick antibodies … but they don’t stick around.
IL-6 and IL-8 drive short-term inflammation.
If they rise too much, they can disrupt germinal center formation -
where long-lived memory B cells are made.
You get quick antibodies … but they don’t stick around.
So, simultaneous COVID + flu vaccination might not be harmful,
but it could change the quality and persistence of the immune response.
This study isn’t about safety - it’s about immunological balance.
but it could change the quality and persistence of the immune response.
This study isn’t about safety - it’s about immunological balance.
Sum:
n = 29 healthcare workers
IL-6 ↑ in most participants
IL-8 ↑ in ~half
Strong negative correlation between IL-6/IL-8 rise and later IgG levels
Coordinated IL-6/IL-8 response = faster antibody waning
n = 29 healthcare workers
IL-6 ↑ in most participants
IL-8 ↑ in ~half
Strong negative correlation between IL-6/IL-8 rise and later IgG levels
Coordinated IL-6/IL-8 response = faster antibody waning
The strength of early inflammation doesn’t just shape how strong your immune response is - it also shapes how long it lasts.
Sometimes, less inflammation means longer protection. @szupraha @ZdravkoOnline @vlvalek @adamvojtech86
Sometimes, less inflammation means longer protection. @szupraha @ZdravkoOnline @vlvalek @adamvojtech86
Schiavoni et al., Cytokine 2025. IL-6 and IL-8 elevations after co-administration of COVID-19 and influenza vaccines are associated with lower anti-spike IgG titers at three and six months post-vaccination. sciencedirect.com/science/articl…
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