Vaksinen er viktig.

Because vaksinen is the definite form of the noun, meaning the vaccine.

In Norwegian, the definite article is often attached to the end of the noun instead of being a separate word in front:

• en vaksine = a vaccine
• vaksinen = the vaccine

Here, -en is the definite ending for many masculine nouns.

In Norwegian, the is usually expressed by a suffix on the noun.

So instead of:

• the vaccine

Norwegian usually says:

• vaksinen

This is very common in Scandinavian languages. English uses a separate article, but Norwegian often adds the definiteness directly to the noun.

Yes. In Bokmål, vaksine is commonly treated as a masculine noun:

• en vaksine
• vaksinen

Some nouns in Norwegian can also be feminine in certain varieties, but for learners, en vaksine / vaksinen is the normal and safest pattern to use.

Er means is / am / are. It is the present tense of the verb å være (to be).

So:

• vaksinen = the vaccine
• er = is
• viktig = important

This is a very basic Norwegian sentence pattern:

• Subject + er + adjective

For example:

• Boken er interessant. = The book is interesting.
• Maten er god. = The food is good.

Viktig is the adjective meaning important, and here it is used after er to describe the subject.

After to be in Norwegian, adjectives often appear in their neuter/single predicate form, which is also the basic dictionary form in many cases:

• Bilen er dyr. = The car is expensive.
• Huset er dyrt. = The house is expensive.
• Vaksinen er viktig. = The vaccine is important.

With viktig, this form is the correct one here.

It may look surprising if you are thinking in terms of languages where adjectives always agree more visibly, but in this sentence viktig is a predicate adjective—it comes after er and describes the subject.

In Norwegian, predicate adjectives do sometimes show agreement, but the form depends on gender/number patterns. Here, viktig is the correct form for this singular noun.

Compare:

• En viktig vaksine = an important vaccine
  (adjective before the noun)
• Vaksinen er viktig. = The vaccine is important
  (adjective after er)

So the adjective can appear in different sentence positions, but here viktig is exactly right.

Yes, in this sentence it is very similar to English:

• Vaksinen = subject
• er = verb
• viktig = adjective/complement

So the pattern is:

• Subject + verb + adjective

That is why it maps neatly onto:

• The vaccine is important.

You would say:

• En vaksine er viktig.

Compare the two:

• En vaksine er viktig. = A vaccine is important.
• Vaksinen er viktig. = The vaccine is important.

So the main difference is:

• en vaksine = indefinite
• vaksinen = definite

You add ikke (not) after the verb:

• Vaksinen er ikke viktig. = The vaccine is not important.

This is a very common rule in Norwegian main clauses:

• subject + verb + ikke + rest

Examples:

• Han er ikke hjemme. = He is not at home.
• Det er ikke sant. = That is not true.

A rough guide is:

• vaksinen ≈ vahk-see-nen
• viktig ≈ vik-tig

A few helpful notes:

• ks in vaksinen sounds like the क्स / ks sound in English taxi
• the final -en in vaksinen is a common definite ending
• Norwegian pronunciation varies a bit by region, but this spelling is straightforward for learners

If you are just starting out, it is enough to recognize the parts:

• vaksin- = noun stem
• -en = the

Yes. In Nynorsk, the equivalent would often be:

• Vaksinen er viktig.

So in this case, the sentence is the same in both Bokmål and Nynorsk. That is useful, because some beginner sentences look identical in both written standards.

Absolutely. This is one of the most useful basic sentence patterns in Norwegian:

• [noun in definite form] + er + [adjective]

Examples:

• Boken er god. = The book is good.
• Filmen er lang. = The film is long.
• Oppgaven er vanskelig. = The task is difficult.

So Vaksinen er viktig. is a very good model sentence for beginners.