Learn Hardcore Russian: Прививка помогает предотвращать многие заболевания.

Прививка is a feminine noun in the nominative singular. It’s the subject of the sentence (the thing that “helps”), so it must stand in the nominative case.

Why is the verb помогает used with an infinitive (предотвращать) rather than a finite form or a different construction?

After помогать, Russian typically uses an infinitive to express the action being helped. Here, помогает предотвращать literally means “helps to prevent.” There’s no need for a conjunction—just помогает + infinitive.

Why is предотвращать in the imperfective aspect, and could I use the perfective предотвратить instead?

The imperfective предотвращать emphasizes an ongoing or habitual ability to prevent diseases in general. You can indeed use the perfective: Прививка помогает предотвратить многие заболевания, which highlights the action as a complete event (“helps to bring about the prevention”). Both are correct, with a slight nuance: imperfective for continuous, perfective for single or whole outcomes.

What cases are многие and заболевания, and why these forms?

Заболевания is a neuter noun in the plural, here functioning as the direct object in the accusative plural (identical to the nominative). Многие is the plural nominative/accusative form of the adjective “many,” agreeing with заболевания.

Could I say много заболеваний instead of многие заболевания, and what’s the difference?

Yes. Много заболеваний uses много + genitive plural and focuses on quantity (“a lot of diseases”). Многие заболевания uses an agreeing adjective and often stresses that “many specific diseases” are prevented. Nuance: много = general amount; многие = many individual items.

Why isn’t there a preposition like от (“from”) before предотвращать? English needs “prevent from,” right?

In Russian, предотвращать already includes the sense “to prevent,” so it directly takes its object in the accusative. You don’t need—and shouldn’t use—an extra preposition like от here.

What’s the difference between прививка and вакцинация?

Прививка refers to the inoculation or the vaccine dose itself. Вакцинация means the overall process or campaign of vaccinating. You “get a прививка,” whereas public health officials organize вакцинация.

Where is the stress in прививка, and why does that matter?

The stress is on the second syllable: при-ВЙ-вка. Correct stress in Russian is crucial because shifting it can change the word or make it hard to understand.

How would I say “Vaccines help prevent diseases” using the plural вакцина?

You can say: Вакцины помогают предотвращать заболевания. Here вакцины is feminine plural, so the verb becomes помогают. You can also add многие заболевания if you want to emphasize “many diseases.”

Can I express this idea in the passive voice, like “Diseases are prevented by vaccination”?

Yes. Use the passive reflexive form: Многие заболевания предотвращаются прививкой. Here предотвращаются is the passive present, and прививкой is in the instrumental case to mark the agent.