Professor Žvirblienė discussed different COVID-19 vaccines and listed their pros and cons

As the professor said, the development of vaccines against coronavirus, a new type of vaccine was developed much sooner. At that time, the old vaccine formats are severely delayed.

“It is such a somewhat paradoxical situation that the vaccine formats we have known for decades are delayed and so far neither Europe nor the United States have approved such vaccines, or even completed clinical trials. Another traditional format is recombinant proteins or pathogen components in the vaccine, which we do not yet have registered in the world. Vaccines of this type are available against hepatitis B or human papillomavirus. Some are already close to registration, but not yet in use, ”said prof. A. Žvirblienė.

Inactivated vaccines

So far, there are no inactivated vaccines in Europe, but at least 2 such vaccines have been registered and used in China, and this type of vaccine is also registered in Russia. The principle of producing inactivated vaccines is not a new invention – the virus is cultured, then killed, usually using chemicals, and then the dead virus, along with adjuvants, is injected into a human. Adjuvants are immune enhancers that enhance the immune response.

“I think the format of such a vaccine would be acceptable to many people because we know them. And at the moment, children are vaccinated with an inactivated polio vaccine, and the flu vaccine is also being developed in this way. Also, the advantage of such vaccines is that they are stored at 2-8 degrees. However, only one vaccine is being developed in Europe, Valneva, which has so far completed only stage 1-2 clinical trials, which is far from registration, ”said the researcher.

Protein vaccines

They contain S protein. The antigen-S protein is created by genetic engineering. The vaccine uses adjuvants to boost the immune response. S protein with adjuvants elicits an immune response, then neutralizing antibodies are formed. This is a traditional, well-known format. This type of vaccine has been on the market since 1990.

They are stored under normal conditions, only need a temperature of 2-8 degrees. However, these vaccines are not yet on the market and are undergoing phase 3 clinical trials. Closest to registration, according to prof. A. Žvirblienė, is a Novavax vaccine, we may have the opportunity to get vaccinated soon.

What we have now in Lithuania are new vaccine formats. One of them is adenovirus-based.Vaxzevria“And”Johnson & Johnson”, Another completely new type – based on RNA.

COVID-19 vaccines

COVID-19 vaccines

New types of vaccines are vaccines based on DNA viruses

One of the new types is the Vaxzevria and Johnson & Johnson vaccines. They contain adenoviruses with the SARS-CoV-2 S protein gene inserted. Non-hazardous human or monkey adenoviruses are used. These enter the cells, producing the SARS-CoV-2 protein (S protein), and the latter elicits an immune response.

“It simply came to our notice then. It can infect cells, it is necessary for it to enter the cell and develop immunity, but it cannot multiply. “How many of those virus cells we get with the vaccine, how many remain, do not increase,” said the VU professor.

Another feature of these vaccines is that different adenoviruses are used for different vaccines. Vaxzevria, for example, is a monkey adevonirus.

“The fact that there is a monkey adenovirus out there should not be very scared because it is taken so that there is no response from our immune system against it. This means that people would not be exposed to this virus. We already have immunity against many human adenoviruses. Johnson & Johnson is a human adenovirus, but one that is not widespread and against which humans do not have immunity. “Sputnik V uses two different human adenoviruses,” she said.

They are stored under normal conditions – at a temperature of 2-8 degrees, so the cost of vaccines is low, known technology. Mass vaccination with these vaccines has already begun.

COVID-19 vaccines

MNA-based vaccines

This is a completely new format. They contain the genetic material SARS-CoV-2, which is the reference RNA. This substance enters the cells, they produce the S protein, and it triggers an immune response. No additional adjuvants are needed as the immune response elicited is already strong enough. To facilitate entry into our cells, the RNA molecule is packaged in a lipid capsule.

However, storage of such vaccines is not easy because the RNA molecule is unstable – they require a temperature of -70 degrees for long-term storage. Mass vaccinations with this type of vaccine have also been launched.

Priority will be given to those vaccines that can be modified according to new strains

RNA vaccines – “Pfizer-BioNTech“, „Modern“, A gift from the unregistered” Curevac “.

Prof. A. Žvirblienė reminded that Lithuania alone does not participate in negotiations on vaccines – they are purchased by the decision of the European Commission. Europe is still negotiating with Novavax and Valneva. The total amount of vaccines ordered is over 2.6 billion.

COVID-19 vaccines

“Contracts were made even when no one knew which of these vaccines would be effective, which were better, which were worse. As a result, the European Commission has sought to build a portfolio of diversified vaccines. They are usually distributed according to population, but each country has the option to purchase a little more or to give up some vaccines. Lithuania’s position has always been that additional doses need to be ordered, as was the case with Pfizer. This vaccine has been ordered really well, about 3 million. doses, only the delivery is slightly delayed “, said prof. A. Žvirblienė.

The current concern is new variants of the virus or otherwise known strains. According to the researcher, the priority vaccines were selected RNA and protein vaccines as the most suitable for booster vaccination. The European Commission has signed a preliminary agreement with Pfizer & BioNTech for almost 2 billion euros. doses. Prof. According to A. Žvirblienė, perhaps so many of them have been ordered to be shared with other countries of the world.

At a conference of immunologists, the professor listed the pros and cons of different vaccines.

mRNA vaccines (Pfizer & BioNTech and Moderna)


– High efficiency, confirmed in real conditions;

– Protection lasts for at least 6 months. after two doses;

– Ability to quickly modify if there are other strains of the virus.


– New format, no long-term security data;

– Complex storage, transportation, required cold chain.


Adenovirus vaccines (Vaxzevria and Johnson & Johnson)


– Proven efficacy in real conditions;
– Simple storage conditions.


– New format, no long-term security data;
– Not suitable for booster vaccination against new variants.

Protein-adjuvanted vaccines (Novavax and Sanofi)


– Traditional format used for more than 30 years.


– Prolonged production technology, no registered vaccines;
– New adjuvants that do not have long-term safety data.

Inactivated virus vaccines (Valneva)


– Traditional format used for about 100 years;


– The effectiveness of vaccines registered in China is only about 50%.

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