Across
- 3. bacteria
- 8. not proved idea
- 10. system fight protect
- 11. hard difficulty
- 12. Covid-19
Down
- 1. injection
- 2. 100 years
- 4. a long time ago in 20s 30s
- 5. many people are sick a the same time
- 6. a way of doing things
- 7. a medicine
- 9. time period