The cCancer is a very dangerous disease whothat killeds millions of people every year.

Since cancer is a category, you wouldn't use The. Who doesn't work because it's not a person. Tensing for kill and million to present since you specify every year.

Our immune system sometimes can't be able to recognize it and can thinks therey are good celluls.

Cut out some unnecessary words and corrected there to they.

The cancer then spreads in the body thanks to cancerous celluls which grow up.

Can cut it down to just this and have the same meaning.

The cancer is saying to our body "Everything is good, there's nothing to look at there" and the immune system is blind to recognise it.

Minor cleanup. To to indicate direction of verb and here instead of there.

There's a treatment against thate disease whothat already exists, but it can have badnegative effects for our body and can hurt us.

Bad is ok, but negative works better here.

The scientistsvaccine's purpose is to train our system immuneimmune system to recognise those anomalies in our bodies and to fight against it.

Think you mean vaccine here. Word order correction.

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A vVaccine for cCancer

Title capitalization rules

The cCancer is a very dangerous disease whoich/that killeds millions of people every year.

Speaking in general = cancer (no "the")

"Who" is reserved for people

No reason to use past tense here (kills)

Our immune system sometimes can't be able to recognize it and can thinks therse are good/healthy celluls.

"Can" already has "able to" built into it.

I can = I am able to

The cCancer spreads in the body thanksdue to cancerous celluls which grow upin size.

I would use "thanks to" for more positive subjects, but it should also be avoided in scientific texts.

Children "grow up" (as they age), but things just getting larger in size simply "grow"

The cCancer is sayingignalling to our body, "Everything is good, there's nothing to look at there," and the immune system is blind to recogniseing it.

Cancer is not actually speaking, and "signalling" is the biological term described for cell communication

There's a treatment against thate disease whoich/that already exists, but it can have bad effects for our body and can hurt uharmful side effects.

"Side effects" is how we describe the non-desirable effects caused by a treatment.

However, diseases like the flu or smallpox have been tpreavented by vaccines.

Vaccines are generally preventative medicines, and are so for both the flu and smallpox (e.g., they are not effective as cures for these examples)

The scientists's purposegoal is to train our system immuneimmune system to recognise thoese anomalies in our bodies and to fight against ithem.

Personally, I think there will be a vaccine in athe near future.

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