How quickly could COVID-19 vaccines stop the pandemic?

 

The novel coronavirus (COVID-19) was announced as a global pandemic by the World Health Organization (WHO) on the 11th March 2020 [1]. Since then, thousands of lives across the world have been affected by the disease, as well as measures to control the pandemic. In December 2020, WHO approved the first COVID-19 vaccine under Emergency Use Listing (EUL), which is the Pfizer/BioNTech Comirnaty vaccine. Since then, many other covid-19 vaccines have been subsequently approved, including AstraZeneca, Janssen, Moderna, Sinopharm, Sinovac, etc [1]. While vaccination programs have been rolling out and larger groups of our population have been vaccinated. We come to address an important question – how quickly can  COVID-19 vaccines stop the pandemic? How much do you know about the situation of COVID-19 in Malaysia?

The ideal vaccine

The ideal vaccine should be safe, efficacious, cheap, easy to administer, have thermal stability, and provide long-term immunity [2,3]. Sounds too good to be true? However, since the development of vaccines started in the 18th century, all vaccines have to go through the lengthy process of being tried and tested, until it has proven to be safe and effective before they could be used by the general public.

The Emergency Use Listing procedure (EUL) is a way to speed up this process in view of public health emergencies. Under this protocol, researchers and public health specialists assess the available data on these unlicensed vaccines and weigh the risks of administering the vaccine, versus not administering the vaccine [4]. Of course, these vaccines still have to go through a safe manufacturing process before their release and approval. No one can tell for sure how long these vaccines provide immunity, nor can they release guarantees about their safety. Under the EUL, only time will give us the answer.

How to stop a pandemic – herd immunity, endemic model?

Vaccines help our body recognize the pathogen and fight against it before it could cause us harm. By doing so, vaccines also prevent the spread of the disease since the pathogen’s disease-causing ability has been halted in a vaccinated individual. Herd immunity is achieved via this means. When a large proportion of a population is already immunized against the illness, even if someone gets infected, the pathogen will not have an opportunity to spread. It is meant to eradicate infectious diseases in a population, as well as to protect those who have contraindications against vaccines – immunocompromised individuals, or individuals with severe allergic reactions.

The proportion of the population required for herd immunity depends on the disease spreading ability. For instance, Measles was completely eradicated when 95% of the population was vaccinated. However, until today, WHO has not released a statement on what is the proportion of the population needed to achieve herd immunity against COVID-19. There are several reasons behind this, one of them being the different kinds of vaccines provided and that the duration of immunity each of them provide is still unknown.

Can covid-19 vaccine stop the pandemic?

Youyang Gu is a data scientist from the United States who came out with a COVID-19 forecasting model for herd immunity and it received widespread popularity and attention. He initially estimated that the herd immunity for COVID-19 will be achieved in the Summer of 2021, with the threshold of 60-90% of the population being vaccinated. However, he later changed his forecasting model to focus on when things will return to normal. He changed this in view of anti-vaxxers, new corona variants, and delayed vaccinations in children [5]. These factors all hinder the achievement of herd immunity.

However, it does not mean that the Covid-19 vaccines are useless. Studies showed the Pfizer-BioNTech vaccines provide up to 95% efficacy for adults who received 2 doses. The AstraZeneca vaccine also shows 100% effectiveness in preventing severe illness and a 76% chance of reducing symptomatic illness 2 weeks after completion of 2 doses [6].

In other words, covid 19 vaccines alone cannot stop the pandemic. It also cannot speed up the process of ending the pandemic. After more than 2 years since the outbreak of COVID-19, humans have started to co-exist with the virus and life has started to resume back to normalcy. This is due to previous public health measures taken, as well as the reduced risk of severe illness thanks to the vaccines.

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