New COVID-19 Vaccination Strategy Suggests Targeting Potential Superspreaders First

Researchers have unveiled a COVID-19 vaccination strategy addressing the question of who should be vaccinated first and have suggested focusing on the locations a potential superspreader visits as well as vaccinating all contacts.

With thousands of scientists around the world racing to develop a vaccine for COVID-19, policy makers may need to decide who is at the front of the vaccination queue if initial supplies are limited. Researchers at Macquarie University (Sydney, Australia) may have a solution once a COVID-19 vaccine is ready. The researchers have developed a theoretical model for a new vaccination strategy that would have the biggest impact - with the least amount of resources - on suppressing the spread of the coronavirus by identifying locations visited by people who are most likely to become so-called superspreaders, and vaccinating them. A superspreader is someone who transmits an infectious disease to an unexpectedly large number of other people.

The research team used anonymized location data for the pre-pandemic movements of 600,000 people in Shanghai and Beijing who were on a messaging app called Momo. The team analyzed a staggering 56 million location visits in just 71 days. The researchers then calculated all the other people the superspreaders would have come in direct and indirect contact with and then extrapolated these trends to develop a model to test the theoretical effectiveness of a vaccine strategy.

Using the location data, they ranked people into six classes by the number of places they’d visited - the higher the number the more contacts. For example, Class 1 meant the person had only stayed at home or visited local shops and been in contact with up to five people. A person in Class 2 would have also gone to a coffee shop or a bus stop and been in direct and indirect contact with up to 15 people. A Class 3 person would have gone to a local train station or the office, a small park or a swimming pool and been in close proximity to up to 25 people, whereas a Class 6 person had visited highly populated public places like universities, airports and stadiums and potentially been in direct and indirect contact with more than a hundred people. The Class 6 people are clearly more likely to become superspreaders.

If this vaccine strategy is to be put into practice once a COVID-19 vaccine is ready, the researchers emphasize the importance for public locations such as restaurants, cafes, clubs, shops, sporting and entertainment facilities to generate an accurate list of patrons so that they could be traced and vaccinated.

“Focusing on the locations where a potential superspreader visits and vaccinating all direct and indirect contacts in the cluster at those locations is the most effective method,” said Professor Bernard Mans, of Macquarie University's Department of Computing. “We found this approach would be as good as vaccinating identified superspreaders based on an accurate contact list and significantly better than random vaccinations.”

“Our research shows that to be effective (and realistic), it’s not about who exactly a superspreader has been in contact with 24/7 but where they’ve been that should be the focus of vaccination,” added Mans.

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Macquarie University