Bermuda Post

Saturday, Jan 23, 2021

Dr Carika Weldon on how COVID-19 vaccine works

Dr Carika Weldon on how COVID-19 vaccine works

Dr Carika Weldon shares information about how the COVID-19 vaccine works, how it was fast-tracked, and the first viral genome sequencing data.

As we all know, Bermuda’s COVID-19 vaccination program started yesterday, after vaccines arrived on island last Friday.

How the mRNA vaccine works

A vaccine typically uses a dead or weakened version of the virus to trigger the body’s immune system to create the antibodies against it. Antibodies are the body’s line of defence against any foreign intruder. Overall, they lead the body to trigger an immune response resulting in the destruction of the 2 disease-causing agent. If a vaccinated person gets infected with the disease, their body is equipped to fight it off fast and prevent sickness. Although most people do not get sick, some still do as the weakened virus can still cause disease. This method has been used since 1796.

To address this issue of vaccination causing the disease, mRNA vaccine have been pursued since the year I was born, in 1990. Using this method prevents someone getting the disease as it gives your body the instructions needed to create a small piece of the virus. This small part that your body will trigger the immune system but cannot give you the disease.

mRNA is a type of RNA, or ribonucleic acid, that is naturally occurring in our bodies. The m in mRNA stands for messenger and plays a central role in how our body operates.

We have all heard of DNA. DNA is the code of life. It is kept safe in each cell in the nucleus to prevent harm or damage. DNA holds the instructions on how to make every part of our body in the form of protein. In order for DNA to make protein 3 the message needs to be carried from the nucleus to the protein making part of the cell; this message is carried by mRNA. This whole process is called the Central Dogma of Molecular Biology.

Dr. Carika Weldon

I will use a cooking analogy to explain this further. We all have our treasured family recipes that have been passed down generation to generation. This cookbook is kept extremely safe as we want to pass it down further to future generations. This cookbook is like our DNA. I know in my family, farine pie is our secret family recipe. Although as nice as the recipe is on its own, we cannot eat the recipe book with the instructions. We have no make the farine pie in order to eat it.

Bearing in mind that we do not want to put the safety of the cookbook at risk, what we do is copy, or write, or transcribe, the same instruction onto an index card. This way we can get the recipe but do not have to worry about destroying the treasured cookbook. We can also even make multiple copies of this recipe on the many index cards and share with the whole famiy. The index card copy of the recipe is like our mRNA.

Now again, having these mobile versions of the recipe is safer, but we cannot eat it. We must still translate the instructions into a tangible form of the farine pie we so love. This involves adding step by step what is needed and ultimately we have the finished product. The farine pie is like all proteins in our body, which are the final products our DNA is holding the instructions for.

This process happens for each and everything made in our body. It is happening right now as I speak. mRNA is the key to it all happening as otherwise the key DNA instruction would not make it to the place where the protein can be made.

A vaccine’s aim is to provide active acquired immunity. It is active, as opposed to passive, because your body has to do some work to make you immune. It is acquired as its specific to infectious diseases your body has fought before, as opposed to innate which is a more general to anything that is foreign in your body. The vaccine Bermuda is currently using for its vaccination program is the Pfizer mRNA vaccine. It provides the instructions to make the outer spike (or S) protein of COVID-19 virus. This spike protein coats the outside of the 5 virus and is how it latches to the respiratory tract of those with COVID-19.

By providing the instructions for making part of the virus, our bodies can make the Spike protein ourselves, and then trigger the immune system to create antibodies for any potential future infections.

As you may know, I along with the leaders of our country, received the vaccine on live TV. I am feeling fine, and only suffer from a sore arm where the needle entered my arm. Our healthcare professionals have a very thoughtful safe process which utilizes best practice. This includes a retractable needle.

During my PhD days I had to routinely use a syringe and needle for some of my experiments. These were not retractable and unfortunately a few times I stuck myself with the open needle. It was painful, happened quicky and ultimately stopped my experiments for the day. I commend the Ministry of Health for making the decision to avoid this potential harm.

How the mRNA vaccine was fast-tracked

Only a year ago, the world was what we call normal, and we had only just heard about a new virus that was affecting China. Today we have a vaccine that can fight against this virus and this is a true feat of many decades of science. There are concerns on how these vaccines could approved so quickly and the following points will address this.

Academic research on coronaviruses and mRNA vaccines has been ongoing for decades. As stated before, mRNA vaccines have been studied since 1990. Coronaviruses like SARS and MERS have been studied for decades as well. Once the new SARS-CoV-2 sequence was published in January, the work could for this specific vaccine could be started. This is also why COVID-19 PCR testing was available a few days after the sequence was shared. Another factor that usually stalls research is the lack of funding. Due to the pandemic status, this barrier was practically non-existent.

Safety and efficacy trials which usually happen subsequently, happened concurrently. Other phase 1 and preclinical studies that showed mRNA vaccine platforms were safe was used to approve this approach. Just like every other scientific and medical advancement, Pfizer's large study had to undergo external peer review and another external review to be published in the prestigious New England Journal of Medicine. The goal of each of these independent review teams is to scrutinize the data inside and out to identify problems before giving approval. It is highly unlikely that all of them overlooked a problem related to safety and efficacy.

Manufacturing and distribution planning happened concurrently with the trials. With much anticipation that the vaccine would be approved at some point, these steps were already discussed to ensure quick turnaround from approval to distribution.

Emergency approval given due to urgency – same as all COVID-19 test kits. Approval not given if unsafe or risks outweigh benefits. Two independent mRNA vaccines 8 produced by competing companies both showing safe data also strengthened the approval process.

Viral genome sequencing

There are three types of testing WHO recommend: RT-qPCR test, which we currently used to diagnose infection, serological or antibody testing, which is currently used to aid epidemiological investigations, and viral genome sequencing.

I am excited to inform that Bermuda has its first viral genome sequencing data and that I will share some key findings thus far.

Just as we can identify each person with their unique fingerprint, each person’s DNA is also unique and can identify them. Viruses don’t have fingers of course, but they do have DNA or RNA that is unique to each one. By doing viral genome sequencing, we can tell strains apart and know how the virus has spread in our community and across the globe.

On October 27th Bermuda had British Airways flight which eventually ended up having 10 positive cases. To investigate this mini-outbreak samples sent to Public Health England for viral sequencing. This includes samples from the flight, along with 12 other samples from around the same time. A total of 21 samples were sent, ranging from cases identified between October 27 – November 18.

Initial analysis of the results show that 8 strains were present on island during this time, with all being imported. 5 of the strains have been imported from the US:

B.1.2
B.1.234
B.1.243
B.1.361
B.1.369

2 from the UK:

B.1.160
B.1.177

and 1 from the Asia:

B.1.36

None of the two UK strains are the new variant strain (B.1.1.7) that has caused the new lockdowns in the UK. Both strains identified at the time are both common strains circulating in the UK since March 2020.

Oxford nanopore sequencing will be performed on a portion of the positive samples from mid-November to December, when Bermuda experienced an outbreak in social settings. We will also look to routinely sequencing positive cases to understand how if any further mutations have occurred on island, and aid epidemiological investigations. In addition, samples each month will be sent to CARPHA for sequencing verification, in a similar manner that regular COVID testing is cross verified at CARPHA.

As we continue on with this marathon fight against COVID-19, now having more tools in our toolkit, let us all do our part by following the guidelines that have gotten us all this far, together.

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