Fri | Sep 24, 2021

Facts about the AstraZeneca vaccine

Published:Wednesday | March 3, 2021 | 12:10 AM

Vaccination has proven an undeniable success in the public health toolkit to reduce the burden of infectious disease in Jamaica as well as globally. Immunisation, the process by which a person becomes protected against a disease through vaccination has proven to be one of the most successful and cost-effective health interventions ever.

Not only is vaccination tried and tested with vaccines in use for more than 200 years, vaccinations have also led to a substantial reduction of illness and death from diseases, such as measles, diphtheria, whooping cough, and newborn tetanus.

Jamaica is expected to get 50,000 doses of the AstraZeneca vaccine tomorrow and some 14,400 doses by next week from the COVAX (COVID-19 Global Access) Facility. The Government has announced that it has reached a deal with the African Medical Supply Platform for the delivery of 1.8 million doses, starting next month.

COVAX brings together governments, global health organisations, manufacturers, scientists, private sector, civil society, and philanthropy to provide innovative and equitable access to COVID-19 vaccines.

Among those to receive the vaccines are our front-line workers, including nurses and doctors, and then to our vulnerable persons, chief among those are persons 60 years and older.


1. Storage and distribution:

The Oxford/AstraZeneca vaccine, also known as ChAdOx1 nCoV-19, or AZD1222, is a viral vector vaccine. Scientists used an adenovirus, originally derived from chimpanzees, and modified it with the aim of training the immune system to mount a strong response against SARS-CoV-2 (the virus that causes COVID-19).

One key characteristic of this vaccine is that it can be stored at 2-8 degrees Celsius (so, in a normal fridge). This is distinct from some of the other COVID-19 vaccines such as Pfizer’s mRNA vaccine which must be stored at ultra-cold temperatures. So the AstraZeneca vaccine can be widely distributed with relative ease.

Additionally, AstraZeneca has multiple supply chains. Around the world they have multiple manufacturing sites, partners from whom to source ingredients, and distributors who can deploy the vaccine. These partnerships will accelerate production and distribution.

2. Safety and efficacy in people over 65

Phase two human trials tested safety and immune responses of the AstraZeneca vaccine, including in people over 65. The vaccine was found to be safe, showing just some mild and moderate reactions, and it induced similar immune responses across age groups.

There are no specific safety concerns, especially based on overseas data and the vaccine induces good immune responses, which is a positive indicator it could be effective in the elderly population.

3. Timing of doses

In initial studies, the vaccine’s efficacy was 62 per cent with two standard doses. However, there was some variability depending on the dosage and timing.

Since then, scientists have asked questions about the optimal dose and interval. A preprint manuscript in The Lancet shows the vaccine demonstrated 82.4 per cent efficacy after two standard doses three months apart. The efficacy was lower if the doses were closer together: 54.9 per cent if the interval was less than six weeks.

4. Protection against different strains

As viruses mutate and give rise to new variants, this can affect how well certain vaccines work against them.We have seen this with the B.1.351 variant of SARS-CoV-2, originally identified in South Africa.

Following a multi-centre clinical trial in South Africa, researchers concluded two doses of the AstraZeneca vaccine had minimal efficacy in mild to moderate COVID-19 cases, specifically due to the B.1.351 variant.

There is still hope the vaccine will be effective against more severe cases of COVID-19.

5. Can it reduce transmission as well as disease?

This question has been asked of all COVID-19 vaccines, and emerging data for the AstraZeneca vaccine is encouraging. This vaccine may block transmission after a single dose.

The researchers derived this data by taking weekly nose swabs from both symptomatic and asymptomatic cases and testing for the presence of the virus. They observed a 67 per cent fall in swabs positive for the virus after one immunisation.

This data suggest the AstraZeneca vaccine also has potential to substantially affect virus transmission, by reducing the number of highly infectious people in a population.

Sources: World Health Organization, Ministry of Health and Wellness,,