Are new vaccines against Covid-19 still necessary?

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It is estimated that

the supply of vaccines against Covid-19

worldwide, and that the coverage target of the World Health Organization (WHO) of at about

.

One of the planned strategies is to

the available vaccines, as foreseen in the COVAX program (Covid-19 Vaccines Global Access), but some experts support the development of

They try to answer this question

, a researcher at the Finnish Institute of Health and Welfare (Helsinki) and chair of the WHO Strategic Advisory Group of Experts (SAGE) for vaccines against Covid-19, and

, Professor at the Lee Kong Chian College of Medicine in Singapore, specialist in emerging viral diseases and coordinator of the SAGE working group.

Both take a voice in an editorial published by

(

), along with two vaccine trials that use technologies other than those used massively.

against Covid-19

have been developed or are still in development , of which

after conditional approval by regulatory authorities, or under the qualification of 'emergency use' by the WHO.

have been used in them

: messenger RNA [mRNA], viral vector, inactivated whole virus, protein subunit and plasmid DNA.

Several of the protein subunit and inactivated whole virus vaccines

to enhance the immune response.

Each vaccine, its advantages

"There are many reasons to develop a range of vaccines against Covid-19 that are available throughout the world in

. Each vaccine product has different

, so before making political decisions there are consider multiple factors", argue the authors of the editorial, ensuring that various countries and health settings

from products made by different technological platforms, as well as various subpopulations and specific age groups.

According to these experts, efficacy and safety, as evaluated in phase 3 trials,

that a country needs to acquire and introduce new vaccines against Covid.

"Additional important factors are ease of scheduling,

, need and frequency of boosters, cost,

cold chain

, manufacturing scalability, acceptance of the community and the scope of

For this reason, they welcome the vaccines described in two articles of the

.

One corresponds to the trial led by

, director of clinical research at the biopharmaceutical company Medicago, which has involved researchers from Canada, Argentina, Brazil, the United Kingdom, Belgium and the United States.

The other article collects the results of the trial led by

from the Laboratory of Pathogenic Microbiology and Immunology of the Chinese Academy of Sciences (CAS), with the participation of China, Indonesia, Uzbekistan, Ecuador and Pakistan.

No extreme cold chains

Both Covid-19 vaccines are produced using new technology platforms:

is developed with plant-based coronavirus-like particles, and

is based on dimers of the virus's receptor-binding domain (RBD).

"Both have the advantage of

, which facilitates their use in primary care, as well as in low/middle income countries that should be included in phase 3 of their trials," they comment. in the article, noting that the time frame of both trials

, before the omicron variant and subvariants appeared.

vaccine

(tested in Argentina, Brazil, Canada, Mexico, the United Kingdom and the United States), which is being evaluated in a two-dose regimen, is a

that expresses the SARS spike glycoprotein -CoV-2 ancestral, combined with the adjuvant system that has been named AS03.

Its

, confirmed by polymerase chain reaction, was 69.5%.

analysis

, the overall efficacy of the vaccine in preventing moderate to severe disease was 78.8%, and among participants who were seronegative at baseline, the efficacy of the vaccine at any stage of disease it was 74%.

"Interestingly, the median viral load among vaccinated participants who continued to test positive for Covid-19 (breakthrough cases) was

for new cases (incident cases) of Covid-19. 19", comment the authors.

The

, carried out in Ecuador, Indonesia, Uzbekistan and Pakistan (efficacy and safety evaluations) and in China (safety evaluation only), evaluates the

, with a regimen of three doses.

During the 6-month follow-up period, vaccine efficacy against symptomatic disease (confirmed by PCR with an onset of at least 7 days after the third dose) was 75.7%.

Against severe/critical disease the efficacy of the vaccine was 87.6%.

Most of the new cases appeared when delta was the dominant variant.

Vaccines and long term

The researchers point out that both trials include mainly

, so

, who are the priority group for vaccination according to the WHO roadmap,

such as the elderly, pregnant women, and immunocompromised patients.

"Post-introduction surveillance of the vaccine will be of paramount importance in monitoring its

, in various subpopulations and healthcare settings," they note, recalling that the WHO has published a

after the introduction of a vaccine.

Until these are carried out, it will not be known if the new products will improve the available anti-Covid arsenal.

"The

during the pandemic

argue the authors, who think that the next generation of vaccines against Covid-19 should have a

to provide cross-immunity against the SARS-CoV-2 variants, provide longer-lasting protection and be easier to

.

"We must remain agile to perfect the use of vaccines against Covid-19 and to

recognizing its benefits," they say, arguing that having more vaccine platforms would possibly help select the most suitable for

age groups, some subpopulations and pregnant women.

The WHO SAGE experts also speak of the possibility of

to take advantage of the benefits of each of the technological platforms and, finally, point out the "

and transmission of currently available vaccines" , which is further reduced in the context of the emerging subvariants of omicron.

"Therefore, to slow the circulation of the virus and

, new vaccines are needed that have a substantial effect in reducing mild infection and transmission, even as the world tries to learn to live with SARS-CoV-2", reads the editorial.

Nohynek and Wilder-Smith recognize that vaccine developers and manufacturers face difficult tasks, and they are committed to continuing to search for the

and control the health and socioeconomic consequences of sudden waves.

They end by praising the decision of the representatives of the

mRNA10 technology centers, "as a sign that countries and regions are motivated to be self-sufficient, not only to plan and participate in key clinical trials, but also to design and manufacture vaccines that better meet the

"And they assert that these technological centers must adopt technologies beyond messenger RNA.

The data of the new vaccines

dropdown

CoVLP+AS03 is the

.

The authors of the essay published by the

have detailed some of the characteristics of this plant-based biopharmaceutical product.

They explain that, although the processing and subsequent purification are similar in all recombinant vaccines, the previous processes in the case of CoVLP

(as a fertilizer). ) to support the live plant 'bioreactor'.

They note that, like other vaccines, plant-based ones targeting new variants can be

and potentially manufactured at different scales of production.

They believe that the technology will be greatly influenced by the evolution of the pandemic itself and highlight some advantages of CoVLP, such as its

, which would facilitate its use in remote communities and in lower-income countries.

They also point out that the more traditional format of the CoVLP+AS03 can

about some of those currently available (they say, without mentioning the mRNA that has caused mistrust in certain sectors of the population) and that this new Plant-derived vaccine could play a

with other products.

In fact, they are already conducting or planning

with this product developed by Medicago with financial assistance from Canada's Strategic Innovation, Science and Economic Development Fund.

The

, which contains a

of the severe acute respiratory syndrome coronavirus receptor binding domain (RBD), and aluminum hydroxide as an adjuvant, is the subject of the second article published by the

.

Its authors say that the results of the trial offer clinical evidence that an RBD-based vaccine is a

.

They claim to use these molecules "because they focus the

on interference with the receptor binding activities of SARS-CoV-2", which is reflected in the clinical efficacy of this dimeric form.

They also try to unravel in their article "some piece of the puzzle to understand one of the main viral targets used in Covid-19 vaccines".

This phase 3 trial was carried out when

.

At the beginning of 2021, the alpha variant prevailed, which was replaced by the delta variant in the following months.

The high cross-

of ZF2001 (an antigen based on the Wuhan-Hu-1 sequence) against different variants of SARS-CoV-2 is encouraging, according to these researchers.

The vaccine, which is

, showed efficacy of 92.7% against the alpha variant in short-term follow-up and 88.3% in long-term;

efficacy against the delta variant was 81.4% and 76.1%, respectively, and efficacy against the kappa variant was 84.8% and 75.2%, respectively.

The

and the Chinese Academy of Sciences have funded the trial.

Conforms to The Trust Project criteria

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