Back to article overview# The effect of vaccination on the number of positive tests

The Netherlands launched its COVID-19 vaccination programme on 6 January. Two months on, about 1.9 million vaccine doses have been administered and we can see the first signs that vaccination is working. The number of positive tests is lower among groups that have received vaccines than groups that have not yet been vaccinated.

The first signs that vaccination is working can be seen among nursing home residents, who started receiving their first shots on 18 January. A few weeks on we are already seeing a change in the number of positive tests. While the number of positive tests among the population as a whole is rising, the number of infections among nursing home residents has fallen sharply. This is illustrated in the graph below.

The grey line shows the change in the number of positive tests among the population as a whole. The yellow line shows the change in the number of positive tests among nursing home residents. If the line is above 0%, this means the number of positive tests is higher than the 7-day rolling average. If the line goes down but stays above 0%, this means that the number of positive tests is still increasing, but more slowly than before.

If the line is below 0%, this means the number of positive tests is lower than the 7-day rolling average. If the line goes up but stays below 0%, this means that the number of positive tests is still decreasing, but more slowly than before.

The graph shows that there has been a clear change since 16 February: the number of positive tests is growing among the population as a whole (the grey line is above 0%) but decreasing rapidly among nursing home residents (the yellow line was already below 0% and has fallen steadily).

We are also seeing effects among other groups that are currently being vaccinated. The vaccination of residents of disability care homes began on 18 January. There has been a clear change since 15 February, just as in nursing homes. The number of positive tests among residents of disability care homes is decreasing almost every day, while the number is increasing among the population as a whole.

Vaccination of people aged 70 and over who live at home began on 26 January. The difference between the total population and this group is not yet as big as it is between the total population and residents of nursing homes and disability care homes. This is probably because most residents of nursing homes and disability care homes have received one or even two doses, while most over-70s who live at home have not yet received the first dose. Nevertheless, we can see that since 23 February the increase in positive tests among this group is slowing down compared to the population as a whole.

In general, we are seeing a positive effect among all groups that have at least started receiving vaccines.