I am using this dataset to get the % of people vaccinated. The problems is that there is an error in the dataset and the % of people vaccinated drop to zero in some days.
I am trying to fix this error picking the previous value. But I still can't change the dataframe.

```
for x in list(range(0,len(brazil_data_covid.index))):
    if brazil_data_covid.iloc[x]['date'] > datetime.date(2021, 4, 1) and brazil_data_covid.iloc[x]['people_vaccinated_per_hundred'] == 0:
      brazil_data_covid.iloc[x]['people_vaccinated_per_hundred'] = brazil_data_covid.iloc[x-1]['people_vaccinated_per_hundred']

```

How can I tackle this?

![enter image description here](https://i.stack.imgur.com/RxB18.png)