Class 3 – The History and Impact of Vaccination (6/19)

Grammar Focus

  • Present Perfect (experience, recent past)
  • Present Perfect vs. Past Simple

Reading Text

Title: The History and Impact of Vaccination

Vaccination has become one of the most important medical achievements in human history. It has saved millions of lives by preventing deadly diseases. But how did it start?

The first vaccine was developed in 1796 by Edward Jenner, an English doctor. He noticed that milkmaids who had caught cowpox never got smallpox. Jenner took material from a cowpox sore and injected it into a young boy. The boy did not develop smallpox. This experiment marked the beginning of vaccination.

Since then, scientists have created vaccines for many dangerous diseases, such as polio, measles, and influenza. The World Health Organization (WHO) has reported that smallpox has been eliminated completely due to worldwide vaccination campaigns. This disease killed millions of people in the past, but no cases have been found since 1980.

In recent years, vaccination has played a key role in stopping the spread of COVID-19. Governments began mass vaccination programs in 2020. Many people have received the vaccine, and studies have shown that it reduces serious illness and death.

Vaccination not only protects individuals but also communities. When enough people have been vaccinated, diseases cannot spread easily. This is called “herd immunity.”

However, some people have refused vaccines for different reasons. They believe vaccines are unsafe, but science has shown that most vaccines are very safe and effective.

Vaccines have changed the way we live. Many diseases that once caused large outbreaks have become rare. Thanks to vaccination, we have lived longer and healthier lives.

Grammar Explanation

1. Present Perfect

The present perfect describes actions or experiences that happened at an unspecified time before now, or actions that started in the past and continue to the present.

Sentence structure

  • Positive:
    • I/You/We/They have eaten
    • He/She/It has eaten
  • Negative:
    • I/You/We/They have not (haven’t) eaten
    • He/She/It has not (hasn’t) eaten
  • Questions:
    • Have you eaten?
    • Has she eaten?

Uses

  1. Life experience (time not important)
    • I have visited Japan.
    • He has never tried sushi.
  2. Recent past with present result
    • She has broken her arm. (Her arm is still broken)
    • They have just arrived.
  3. Ongoing actions (with for/since)
    • We have lived here for ten years.
    • He has worked at NASA since 2021.

2. Present Perfect vs. Past Simple

Present Perfect Past Simple
Unspecified time Specific time
Focus on result Focus on when
Still true now Finished action

Examples

  • Present Perfect:
    • Scientists have discovered new treatments.
    • I have been to Italy.
  • Past Simple:
    • Scientists discovered penicillin in 1928.
    • I went to Italy in 2019.

Signal words

  • Present Perfect: ever, never, already, yet, just, for, since
  • Past Simple: yesterday, last year, in 2005, two days ago

Summary Chart

Tense Use Case Example
Present Perfect Life experience, recent result He has visited Africa.
Past Simple Completed action at specific time He visited Africa in 2018.

Vocabulary

  1. Achievement
  2. Develop
  3. Disease
  4. Prevent
  5. Inject
  6. Experiment
  7. Campaign
  8. Eliminate
  9. Spread
  10. Immunity
  11. Refuse
  12. Effective
  13. Outbreak
  14. Rare
  15. Science
  16. Serious
  17. Role
  18. Create
  19. Cause
  20. Impact