# How do we count

We are creating a **virtual model** to simulate the process of vaccination. Therefore when we calculate estimated pandemic end date, we can take into account such variables as number of coronavirus cases, pause between vaccination days, number of one- and two-dose vaccines. Such model makes more accurate estimation.

## Our assumption

Our estimated date for each country is calculated based on assumptions that:

- To achieve herd immunity 70% of population has to be fully vaccinated. [1]
- Antibodies that people develop after infection last for six months. [1]
- Two doses of vaccine for every person is needed.
- The COVID-19 vaccine could become a yearly shot as so far it is unknown how long immunity will last after a person is fully vaccinated. [1]
- The current pace of vaccinations continues.

## Calculation

- We are calculating the 5-day, 10-day, and 30-day moving average of vaccinations and infections. You can check the estimation based on the number of days you define in settings.
- For each subsequent day we calculate whether the number of people who have immunity is greater than or equal to 70% of the population.
- People who have been infected with COVID-19 less than six months ago are included in the number of people who have immunity until the day six months have passed. From that day on they need to get vaccinated.
- Revaccination in a year is needed. So herd immunity of 70% of population has to be achieved in less than a year.

## FAQ

### Why is it impossible to calculate estimated date for some countries?

In the calculation we assume that revaccination is needed after a year of the second vaccine dose (assumption statement #4). At the current average vaccination pace it is not sufficient to achieve herd immunity of 70% of population in a year. People who received the second vaccine dose more than a year ago are added to the amount of people with no immunity. So calculation of the date in not possible due to never-ending cycle.