New Zealand’s COVID-19 vaccination status is based on infection likelihood

There are a variety of strategies that have been devised to fight the coronavirus disease 2019 (COVID-19) pandemic caused by a novel coronavirus, namely severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The New Zealand government’s strategy to manage the SARS-CoV-2 delta outbreak was heavily dependent on the frequency at which vaccinations were given. This meant that double-dose vaccination rates grew from 19 percent to 70 percent of the population as of 21 November 2021.

Study: Infection or infection with COVID-19 is a function the status of the vaccine. This was studied using a stochastic model of New Zealand (Aotearoa). Image Credit: LBeddoe/Shutterstock


Scientists discovered that only 5% of COVID-19-infected people needed hospitalization in the fully vaccineed group. After two weeks, a person was considered fully vaccine-free.

The country is transitioning to the COVID-19 Protection Framework. This framework is based on vaccine certificates. The government has relaxed the Auckland border to those who are fully vaccinated or have COVID-19 positive tests that were completed within 72 hours of traveling. It is essential to be aware of the possibility of COVID-19 being transmitted between non-vaccinated and vaccinated individuals.

While contact tracers can be employed to stop onward COVID-19 transmissions they are not able to identify the source of infection. There is no chance of an individual being infected or infecting other people due to their vaccination status.

Utilizing real-world examples, a new study has addressed this research gap and determined the possibility of the number of infections that could be caused by an unvaccinated person. This simulation was performed using a stochastic model that the author had previously developed. The study was published on the preprint server.

A new study

The study’s primary purpose of helping to formulate effective travel restrictions and reopening decisions. Based on COVID-19 vaccination status, the researcher estimated the likelihood of infecting or infecting others. Mathematical tools could play a crucial role in predicting the possibility of this as the frequency of SARS-CoV-2 cases across communities has increased substantially.

A stochastic branching model was used in this study to simulate the effects of vaccinations. The model was seeded with one vaccinated and one non-vaccinated person at a specific time per day. The model was then examined for 31 days. To achieve the best results from the stochastic model the simulation was run 100,000 times for each scenario. The study assumed that an infected COVID-19 person could travel to spread the virus and begin the next epidemic.

Despite the fact that preventive measures were implemented prior to the time the Auckland border was opened for travel, there is an increase in COVID-19-related cases in several places across the country including Waikato and Northland.

The author used stochastic mathematical models to simulate the scenario. The model was basing it on the current vaccination rate for the nation which is 78.7%. According to the District Health Boards’ reports, around 90 percent of the population eligible, including individuals above 12 years, have been vaccinated.

Principal findings

The cumulative probabilities were used to determine the probability of infection among unvaccinated or vaccinated people within 31 days. It revealed the existence of the possibility of a small amount of outbreaks that are large in the first 31 days of an infection that is sown by either vaccinated or unvaccinated individuals.

The odds of the COVID-19 infection expanding beyond the initial instance of vaccinated seeds are greater than those who have not been vaccinated seeds infection. The study revealed that 54% of travelers who are not vaccinated could infect 151 people within 31 days. This finding emphasized the importance of COVID-19 vaccination in the fight against the pandemic.

The study concluded that a traveler who has been vaccinated is nine times less likely to seed an outbreak in a community than non-vaccinated travelers. Therefore, this study has highlighted the importance of travelers to be vaccinated or checked negative prior to travel or both as a necessary step to prevent the spread of further outbreaks.

The mathematical model can track the number of unvaccinated and vaccinated cases as well as the vaccination status of the individuals that cause the infections. This allowed the author to determine the likelihood of infection based on the vaccination status of the infected and infected. The results were obtained by calculating the mean over 100,000 realizations.

According to the study’s author, even though vaccines offer significant protection against infection, those who aren’t vaccinated might be more likely be infected than vaccinated or infected persons. The majority of infections are caused by non-vaccinated people that is around 65 percent of all infections. In contrast, vaccinated individuals are responsible for only 35% of all infections.


These findings highlight the importance COVID-19 vaccination to stop an individual from contracting and spreading an infection. The primary reason behind the spread of COVID-19 is due to unvaccinated people according to the author. This means that vaccinating people who aren’t vaccination-free from areas at risk will help to lessen the spread of COVID-19.

*Important notice

medRxiv publishes preliminary scientific reports that are not peer-reviewed and, therefore, should not be regarded as conclusive, guide clinical practice/health-related behavior, or treated as established information.

Journal reference:

Content Source:

Gemma Wilson

Gemma is a journalism graduate with keen interest in covering business news – specifically startups. She has as a keen eye for technologies and has predicted quite a few successful startups over the last couple of years.

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