Effectiveness of the Vaccine and the Particular Producer Pivotal in the Decision to Get a Booster

Which factors influence the decision for a COVID booster jab? As an experimental online study from ZEW Mannheim together with Cornell University and Indiana University has shown, the efficacy of the booster and the producer of the vaccine, as well as potential financial incentives are pivotal in the decision. “The willingness to get a booster is highest for the Pfizer/Biontech vaccine, followed by the Moderna vaccine. Enthusiasm for the Johnson & Johnson vaccine lagged significantly behind,” says Professor Nicolas Ziebarth, head of ZEW’s “Labour Markets and Social Insurance” Research Unit and one of the study’s authors.

Additionally, an information campaign from health experts reporting that the Omicron variant is more contagious – but less deadly – than previous variants, significantly increases willingness to get a booster jab. On the other hand, the length of protection provided by the vaccine and the potential protection against future variants is considerably less important for individual willingness for the third COVID vaccination. According to Ziebarth, there is an interesting – certainly very US-specific – detail, that there is a significant divide between Democrats and Republicans. The willingness to get a booster jab among Democrat voters sits seven percentage points above, and for Republican voters nine percentage points below, the average.

The conclusions of the ZEW study deliver valuable guidance for future vaccination campaigns. Warnings of particularly contagious virus variants can thus be used to possibly increase willingness to get a booster dose. Furthermore, the gap between supporters of the two political parties shows that it’s necessary to address the population systematically to overcome booster scepticism. However, the study does not make any concrete statements about the extent to which the results can be applied to Germany. “The underlying conclusions could, however, be relevant to German politics,” says Ziebarth. “In Germany, the ‘willingness to get a booster’ will be highest for the Biontech vaccine, too, considering the number of doses administered so far. Also, the most successful vaccination campaigns are those which emphasise high immunity through vaccination and the high risk of infection of the current COVID-19 variant. Especially at the start of the wave of infection in autumn 2023, it will be crucial to campaign for booster vaccinations. So far, only 63 per cent of adults have had their first booster jab; and merely 12 per cent of them got the second booster jab.”

For this study, the researchers surveyed around 550 US citizens who at that time had obtained basic immunisation against COVID-19 through two vaccinations, but had not yet received a booster jab. The survey was conducted in December 2021, a few weeks after the first Omicron variant had been discovered.

As in Germany, vaccination is one of the most important measures to combat the COVID-19 pandemic in the United States. According to the US Centers for Disease Control and Prevention, by mid-October 2022, a little over 72 per cent of the population aged five or older had had basic immunisation, i.e. two doses of a COVID vaccine. A booster vaccination (=third injection) improves immunity even further, but the share of those above the age of 12 years who had received a booster vaccination was considerably lower, at roughly 50 per cent.