Covid-19: Two of the vaccine front runners have already reported promising evidence - so what now?

  • In early results from a human trial, Moderna's Covid-19 vaccine candidate was shown to be 94.5% effective.
  • Scientists say from the detailed findings released, it may have the edge over another candidate which also shows huge promise.
  • Approval for this type of vaccine  an mRNA vaccine  has never been granted before, but the early results are a step in the right direction.

Drugmaker Moderna announced on Monday that its Covid-19 vaccine candidate, named mRNA-1273, was 94.5% effective, based on an early look at the results from its 30 000-person ongoing clinical trial.

The news arrived not long after similar results announced by Pfizer last week, and add to growing confidence that vaccines will help fight the pandemic and might be the best chance for the world to return to normal.

Participants in the trial were randomly given a two-dose regimen of either Moderna's experimental shot or placebo (saltwater) injections. The company's announcement states that their first interim analysis was based on the first 95 participants to develop Covid-19.

According to the data, there were 11 cases of severe Covid-19 in the trial, but none happened in participants who were immunised.

Moderna says its next step is to seek regulatory approval in the coming weeks for the use of the vaccine in the US. It expects to have 20 million doses available in the country and "remains on track to manufacture 500 million to 1 billion doses globally in 2021".

What scientists are saying

Professor Thomas Scriba, deputy director of immunology and laboratory director at the South African Tuberculosis Vaccine Initiative, University of Cape Town, told Health24 Moderna's results are very similar to that of Pfizer's, and echoed his previous comments on the latter's vaccine candidate.

"This is clearly an important and very positive step in a chain of many steps that need to be taken before vaccine vials are available in pharmacies and clinics.

"It is great that two vaccine candidates have shown such high levels of efficacy in interim analyses because the burden of proof from two independent sources is growing. Of course, the same limitations raised in my previous comments still stand – these are results shared is a press statement from a very short period after vaccination.

"The news that the mRNA-1273 Covid-19 vaccine candidate by Moderna is stable for 30 days at 2-8 degrees Celsius and for up to 6 months at -20 degrees Celsius is very important and good news, since these are the kind of transport and storage conditions required for many existing medical products (so they are already in place in many settings).

"Distribution and delivery of a vaccine to those who need it will be easier to achieve under these conditions," Scriba said.

Some experts contacted by Reuters raised the point that the findings reported on Monday with the Moderna vaccine candidate are more detailed.

Professor Bodo Plachter, deputy director of the Institute of Virology at Mainz University Teaching Hospital in Germany, said: "Moderna has the advantage (over Pfizer) that they can already provide detailed findings on aspects such as severe disease, age and side effects.

"The question remains: What will protection look like after three, six or 12 months. It is fair to assume that it will last at least a year but we can't be sure at this point.

"The side effects are within a range that would be expected of many other vaccines, such as shingles vaccine Shingrix."

The severe disease aspect was echoed by Eleanor Riley, professor of immunology and infectious disease at the University of Edinburgh.

She told Reuters: "Although the numbers are small, this trial also gives an indication that vaccination is effective in older and BAME individuals and prevents severe disease, all of which are key to allowing the world to start opening up again.

"The absolute prerequisite for a Covid-19 vaccine is that it stops people becoming ill enough to require hospital treatment and stops people dying. The preliminary data reported here suggest that this vaccine – and by extension, the Pfizer/BioNtech vaccine – will achieve this goal.

"The safety data also look promising. The side effects of vaccination appear to be in line with those typically seen for other adult vaccinations, including the seasonal influenza vaccination which is administered in many millions of doses every year.

"One important unknown is whether this vaccine, or any of the vaccines currently in trials, prevents disease transmission.

"It is likely that vaccines that prevent symptomatic disease will reduce the duration and level of infectiousness, and thus reduce transmission, but we don't yet know if this effect will be large enough to make any meaningful difference to the spread of the virus within communities.

"But, overall, this is excellent news. Having more than one source of an effective vaccine will increase the global supply and, with luck, help us all to get back to something like normal sometime in 2021."

Very good news

Most scientists agreed that the news was encouraging, especially on the back of the Pfizer announcement last week.

Professor Trudie Lang said: "It is very good news indeed to see another vaccine coming through with similar efficacy results as were reported last week from Pfizer. This is also an interim analysis, which means that there were enough cases within the vaccinated volunteers to give statistical significance and allow the team to break the blind to determine who had the active vaccine and who had placebo.

"Here they found that of 95 cases of Covid, 90 had received the placebo and five the active vaccine. These early results suggest that there was a representation across different age groups and diverse communities in the protected group. This is really encouraging and it further demonstrates that a vaccine for Covid is a real probability and that having more than one supplier should help assure better and more equitable global availability.

"This vaccine is also an mRNA vaccine, so many of the same questions remain as we have been discussing with the Pfizer vaccine and these will be looked at carefully by the regulators."

Professor Lang is the director of The Global Health Network, Nuffield Department of Medicine, at the University of Oxford.

Much more data needed

"This announcement from Moderna is a further encouragement that vaccines will be found to not only have an acceptable efficacy, but an efficacy that is much greater than we had anticipated. This press release is more specific than that of others, in that it confirms the numbers in each group, which was able to be guessed at but to have it confirmed is helpful," Professor Stephen Evans told Reuters.

Evans, professor of pharmacoepidemiology at the London School of Hygiene and Tropical Medicine, added: "The range of minor adverse effects reported are unsurprising and typical of almost any vaccine. These reactions tend to be local to where the injection was given and are rarely long-lasting or severe.

"Although they reported efficacy being over 94%, there is statistical uncertainty in this; but based on these data, the likely efficacy will be better than 85% which would be greater than most scientists would have expected.

"This is the first study to report on severe cases and, while uncertainty remains, the finding of no severe cases with the vaccine and 11 cases with placebo is very strong evidence that the vaccine prevents severe as well as mild disease. It is likely that convincing evidence in respect to deaths will probably only be obtained when the vaccine is in use.

"A wide range of people with illnesses and from minority groups were included in the trials as well as substantial numbers of older patients. We will need much more data and a full report or publication to see if the benefit is consistent across all groups, notably the elderly, but this is definitely encouraging progress."

Peter Openshaw, professor of experimental medicine at Imperial College London, said more complete details were needed but the announcement added to a general feeling of optimism.

"This news from Moderna is tremendously exciting and considerably boosts optimism that we will have a choice of good vaccines in the next few months.

"This latest press release is based on a study of 30 000 US adults, including many high-risk or elderly persons. This gives us confidence that the results are relevant in the people who are most at risk of Covid-19 and in most need of the vaccines.

"Moderna have also announced that the vaccine can be kept in a conventional freezer (-20 degrees Celsius) for up to 6 months, and that once thawed the vaccine can be kept for up to 30 days at standard refrigerator (2 to 8 degrees centigrade). This makes the vaccine much easier to deliver.

"In terms of side effects, news is also quite good. The first dose caused injection site pain in about 3% of people; the second dose was associated with transient generalised symptoms in about 10% of people with fatigue, muscle aches and flu-like symptoms.

"This seems to indicate that they got the dose about right with acceptable adverse events. These effects are what we would expect with a vaccine that is working and inducing a good immune response.

"We need more complete details than we have in this press release, but this announcement adds to the general feeling of optimism about vaccines for Covid-19. What we still don't know is how long any protective immunity may last. For that, we will need to wait."

Pfizer first to announce 90%-plus efficacy

Last week, drug maker Pfizer said data from their Phase 3 experimental Covid-19 vaccine, BNT162b2, showed it was 90% effective in preventing infections in volunteers, Health24 reported.

The company and its collaborator, BioNTech, stated no serious safety concerns were found during their large-scale global clinical trials, and they expected to seek US authorisation this month for emergency use of the vaccine.

The data released was based on global data that included the trial site in South Africa, a Pfizer spokesperson told Health24.

"We are pleased to share that the trial in South Africa is going as planned, having already completed recruitment of participants across four sites in Gauteng, Limpopo and the Western Cape," the company said.

While there are still some unanswered questions, such as how long the vaccine will provide protection, international scientists have welcomed the news saying it "is an excellent result for a first generation vaccine".

mRNA vaccines

Moderna and Pfizer's vaccines both use messenger RNA, or mRNA, technology that is designed to trigger an immune response without using pathogens, such as actual virus particles.

This is done by injecting part of the coronavirus' genetic code into the body, which then starts making viral proteins (but not the whole virus).

Should the person who received the vaccine encounter the virus, their antibodies and T-cells (which acts as "natural killers") will therefore be triggered to fight it, thanks to the viral proteins which trained the body's immune system to attack the virus.

Moderna explains that mRNA medicines essentially "instruct a patient's own cells to produce proteins that could prevent, treat or cure disease".

mRNA vaccines still need to be approved

While many studies of mRNA vaccines have taken place, none have been approved before – but the promising early results from Phase 3 trials for both candidates, as well as both being above 90% effective, put them in a good position.

"If mRNA vaccines against Covid-19 gain regulatory approval, this will be a huge validation of the RNA vaccine production platform technology," Zoltan Kis, a research associate at The Future Vaccine Manufacturing hub, at Imperial College in London, told Reuters.

"Using this technology, vaccine candidates can be produced substantially faster in the future to combat virtually any infectious disease, by producing vaccines against both existing pathogens and future, currently unknown pathogens.

"Vaccine candidates can be produced against virtually any disease, because this is a platform technology, meaning that the production process, the purification processes and the formulation processes can remain the same no matter what vaccine or vaccine candidate is produced.

"This is a huge advantage in terms of the speed at which vaccine candidates can be developed and produced in the future.

"In the case of conventional vaccine production technologies, each vaccine required the development of a new production process, whereas in the case of the RNA vaccine production platform technology one process can produce vaccines and vaccine candidates against virtually any disease."

What's next?

This is still early data as both Pfizer and Moderna announced their trial findings in news releases. Therefore, as Scriba explained, detailed data that will allow outside experts to evaluate their claims (peer-reviewed journals) have yet to occur, so the results cannot be considered conclusive.

More than this, the trials are still ongoing and additional data may affect results.

Logistical challenges

If and when a vaccine becomes available to the public, there are many logistical issues to consider.

Scriba previously explained that once a vaccine is licenced for human use by regulators, it would need to be manufactured in large volumes, and distribution networks needed to be established and vaccination programmes would have to be put in place to deliver the vaccine to those who needed it.

"These are all non-trivial endeavours. We have had highly efficacious vaccines for a number of deadly diseases for decades and yet these diseases are still causing many deaths and cases of disease because these vaccines do not reach all those who need them.

"This result is clearly an important and very positive first step in a chain of many steps that need to be taken before vaccine vials are available in pharmacies and clinics," Scriba said.

Additional reporting by Bhekisisa also notes that ensuring that a potential Covid-19 vaccine gets to people who need it – and is effective once they get it – will be challenging in the case of Pfizer's vaccine, for example, especially for countries like South Africa. 

This is because Pfizer's vaccine needs to be stored below freezing temperatures (minus 70 degrees Celsius).

Moderna said its candidate could be stored at a standard temperature of between two and eight degrees Celsius for up to 30 days – compared to its shelf life of six months when kept frozen. Despite this revised storage temperature, the jab still needs to be shipped and transported at minus 20 degrees Celsius.

Director of Vaccines for Africa at the University of Cape Town, Gregory Hussey, told Bhekisisa that except for a few of the ultra-cold freezers at large research institutions, such as the National Institute for Communicable Diseases (NICD), SA is unlikely to be able to afford to buy enough of these freezers (which cost between R150 000 and R235 000 each) to be able to make the vaccine available at community health centres or clinics, or pay for the cold chain systems that are necessary to maintain the vaccines.

South Africa has also not yet managed to secure any doses of candidate vaccines from Pfizer or any other manufacturer, Spotlight recently reported, adding that the country also missed the first deadline to commit to COVAX – an initiative co-lead by the World Health Organisation that aims to ensure developing countries get access to Covid-19 vaccines.

However, spokesman for the Department of Health, Popo Maja, confirmed to Spotlight that although SA had not concluded any vaccine deal, negotiations with manufacturers and COVAX are underway.

What about other vaccines?

While Pfizer and Moderna were the first to announce early results on large clinical trials, the World Health Organization's latest draft landscape of Covid-19 vaccine candidates, dated 12 November, indicates that there are over 40 other candidates in the earlier stages of testing.

Another frontrunner is Johnson & Johnson's Ad26.COV2.S vaccine, which has already commenced its Phase 3 ENSEMBLE trial.

The company announced on Monday that it launched a new late-stage trial in Britain to test a two-dose regimen of their experimental vaccine among thousands of volunteers, Reuters reported.

This trial will run in parallel with its 60 000-person global trial of a single shot of the vaccine, which was launched in September, and is also currently being trialled in South Africa.

*Additional reporting by Reuters, Bhekisisa, and Spotlight.

READ | The latest news on a leading Covid vaccine candidate is promising, but how optimistic should we be?

READ | Cold truth: South Africa won’t be able to store these Covid vaccines. Here’s why.

READ | Leading Covid-19 vaccine candidate to be manufactured in SA

Image: Getty/Tetra Images

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