In 1959, Anton Mayr, a German microbiologist, developed a strain of the smallpox vaccine and began growing it in cells derived from chicken embryos. After several years of transferring the strain to new cells every few days, the virus changed so much that it could not reproduce in most mammalian cells. However, it can trigger an immune response against smallpox.
Mayr aimed to study the evolution of poxviruses, but accidentally developed a potentially safe vaccine against smallpox. The modified Vaccinia was called Ankara (MVA) because the original strain of the virus came from that Turkish city, and the vaccine’s career was short. Gerd Sutter, a virologist at the Ludwig Maximilian University in Munich, said that after smallpox was eradicated in 1980, it disappeared from the freezer.
Now, the virus, further weakened and marketed by the Danish pharmaceutical company Bavarian Nordic, could be the key to catching the largest outbreak of smallpox outside Africa, which has already infected more than 1,000 people. This is the only vaccine that is allowed to be used against smallpox in monkeys, but other, dangerous smallpox vaccines also offer some protection. The United States, the United Kingdom, Canada, and a number of other countries have begun vaccinating people who have been in contact with smallpox, including health care providers and sexual partners. “MBA is very important in this epidemic because it is a non-replicating vaccine and therefore has no side effects like other live vaccines. [virus] Vaccines are being considered, ”said Rosamund Lewis, the World Health Organization’s (WHO) technical director for smallpox.
However, the final outcome of the vaccine will depend on many factors: whether people at risk of infection can be identified and vaccinated, whether the vaccine is as effective as expected, and whether it is sufficient to stop the epidemic. The WHO has so far only supported ring vaccination – the MVA is ideally given within 4 days of exposure, but is recommended for up to 14 days – but according to some scientists, it is very difficult to reach specific contacts in humans. They advocate for widespread immunization campaigns among the most affected population to date: men who have sex with men (MSM).
Hundreds of millions of doses of smallpox vaccines are stored around the world to insure against the spread of the deadly virus by terrorists or in war, and they offer some protection against smallpox. A study conducted in the Democratic Republic of the Congo (DRC) in the 1980’s found that family contacts of people with smallpox were seven times less likely to be infected if they were vaccinated against smallpox. However, the vast majority of smallpox vaccines are still revaccinated. These include rare but life-threatening side effects, such as encephalitis or a progressive vaccine, the spread of the vaccine virus throughout the body, and people with weakened immune systems.
In African countries, 66 people have died of monkey disease this year, but in non-endemic countries it has been mostly mild in recent times. However, most people who become infected live with HIV, which can affect the effects of the vaccine. Given the risks and benefits, “these vaccines cannot be used,” Sutter said.
The non-replicated vaccine from Bavarian Nordic, sold as Jynneos in the United States and Imvanex in Europe, negates some of the risk. A vaccine based on the LC16m8 vaccine is licensed only for smallpox in Japan, and has fewer side effects. “I think these are the ones that will be used [in the new outbreak] because they have a much improved safety profile, ”said Marion Gruber, who will head the U.S. Food and Drug Administration’s vaccine office until October 2021.
Canada and the United States have received an MVA license for use against smallpox and are in talks with the Bavarian Nordic European Medicines Agency (EMA). “I really hope it will be approved in Europe in 1 or 2 months,” says EMA’s Marco Cavalieri.
The UK has been using “unknown” MVAs for several years to vaccinate those associated with imported monkeys. The WHO Strategic Advisory Group of Immunization Experts will issue guidelines in support of the MVA in the coming days, but it also recommends the use of previous vaccines in certain scenarios. However, Cavalieri says, “If [MVA] Available, this will be the starting vaccine.
The exact number remains unclear. “Countries have been reluctant to detail this information with the WTO for the past two decades, but the WTO is now addressing all of them again,” Lewis said. The United States, which supports the development of the MVA, probably has the largest supply. The federal spokesman said the National Strategic Reserve has 36,000 doses, another 36,000 doses will be delivered “in the near future” and the company is storing bulk material for millions of doses stored in the United States. A spokesman for Bavaria’s Nordic said many other countries had ordered their MVA vaccine in recent weeks and the company was trying to send fewer batches to countries “so they can start vaccinating earlier”.
The prevalence of MVA or any vaccine remains a major debate. Given the stigma and nature of the connections that this group faces in many cultures, ring vaccination among MSMs can be difficult. An article published last week Eurosurveillance He said most of those infected in the UK reported having sex with people they did not know or did not want to share.
In the last 14 days, the Canadian province of Quebec has extended vaccinations directly related to monkey disease to men who have had more than two male sexual partners. Another way to address the problem, says Gregg Gonsalves, an epidemiologist at the Yale School of Public Health, “would be to recommend it to people who participate in social activities that are closely related to the infected person, but it will increase the number of mercenaries.” According to Leif Eric Sander, an infectious disease specialist at Charite University Hospital in Berlin, Germany will offer a wider vaccine, but it will not be fast enough for all MSMs.
Reception was also low in areas where contacts of infected people were identified. In the same UK study, 169 of the 245 healthcare professionals recommended by the MVA said they accepted it, but only 15 of the 107 contacts in other groups accepted it. “It’s very difficult to target high-risk groups by balancing the stigma and encouraging vaccination,” said Boguma Titanji, a virologist at Emory University. The politicization of vaccines during COVID-19 has increased barriers, he adds.
It is unknown how well MVA protects people from monkeys. The MVA license in Canada and the United States is based on animal studies, which show that it protects macaques and field dogs, as well as evidence of a strong antibody response in humans. Pairs of DRC studies vaccinated 1,600 health workers with one of two MVA formulas and did not detect monkey smallpox every 2 years during the study period. But there were no control groups, and a health worker who received the vaccine contracted monkey disease six months later. Ira Longini, a biostatrist at the University of Florida who advised the WHO, said: “In fact, we do not know the effectiveness of any of the smallpox vaccines.”
That is why the WHO has called on countries that have introduced the smallpox vaccine to study how effective it is and how to use it well. “If we want to prevent these epidemics and learn something about the effectiveness of these vaccines, we need to work with these protocols and organize them properly,” Longini said. One question is whether one dose of the vaccine, usually two doses given every 4 weeks, is sufficient. This can stimulate more acquisitions and expand supply.
The issue of the share of vaccines is also big. Titanji notes that expectations for the MVA are based in part on DRC data. “If these vaccines are now being used elsewhere, it is a moral obligation to believe that people who have been reported to be battling smallpox for 50 years should also have access to them.”