Monkeys show immunity to coronavirus

Chinese President Xi Jinping walks past ministers in face masks during the opening session of the National People’s Congress at the Great Hall of the People in Beijing on Friday

In the U.S. and United Kingdom, vaccines from Moderna and Oxford University (collaborating with AstaZeneca) are in human trials, and have shown promising early results. However, the researchers cautioned that the results should be interpreted carefully.

"The challenges in the development of a COVD-19 vaccine are unprecedented, and the ability to trigger these immune responses does not necessarily indicate that the vaccine will protect humans from COVID-19", Chen said.

It is not known if the same result occurs in humans but the group says the findings have profound implications for vaccine development and treatment based on immunological responses.

In the desperate early days of the coronavirus pandemic, reports from China that few critically ill COVID-19 patients could be revived after a cardiac arrest led doctors in some countries to consider issuing blanket "Do Not Resuscitate" orders.

The first phase of the recombinant adenovirus type-5 (Ad5) vectored COVID-19 vaccine was carried out at several laboratories by the researchers and included 108 participants between the age of 18 to 60 years. For example, modify the measles virus to produce the spike protein that SARS-CoV-2 uses to infect a cell. These cells then produce the spike protein, and travel to the lymph nodes where the immune system creates antibodies that will recognize that spike protein and fight off the coronavirus. Randomized placebo-controlled studies are needed to clarify the risks and benefits of the decades-old drug in the treatment of COVID-19, the researchers said. Participants received either a low, middle or high dose of the vaccine. These vaccines helped the monkeys develop higher levels of antibodies, which lowered the level of the virus following exposure.

Scientists found that all volunteers well tolerated the doses with no serious adverse events.

"We showed that vaccines induce antibodies, and the vaccinated animals are protected either partially or fully", Dr Barouch said, CBS reported.

Four weeks after the injection, the most common adverse reactions were mild pain at the injection site, fever, fatigue, headache, and muscle pain. "Further research will be needed to address the important questions about the length of protection, as well as the optimal vaccine platforms for a SARS-CoV-2 vaccine for humans". However, these adverse reactions persisted for less than 48 hours.

The researchers tested three doses and said the highest dose seemed to be the most effective. "We selected doses for the phase-2 study mainly on the basis of the safety profile of the candidate vaccines shown in the participants within seven days and 14 days post-vaccination", they note.

The researchers tested the volunteers' blood at regular intervals following vaccination to see whether the vaccine stimulated both arms of the immune system - the one that produces neutralizing antibodies that can fight infection and could offer a level of immunity and the cell-mediated portion, which depends on a group of T cells, rather than antibodies, to fight the virus. While antibodies neutralise the virus outside the cells, T-cell response plays a major role in destroying virus-infected cells.

"Our study found that pre-existing Ad5 immunity could slow down the rapid immune responses to SARS-CoV-2 and also lower the peaking level of the responses". The high pre-existing immunity might also have a negative effect on the persistence of the vaccine-elicited immune responses, they write.

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