Cure worse than disease? Some Covid-19 vaccines may increase HIV risk, scientists warn

A group of researchers in the US is sounding the alarm over several coronavirus vaccines currently undergoing clinical trials, warning that they may increase the risk of contracting HIV in subjects who take them.

At least four of the current batch of Covid-19 vaccines in development at the clinical trial stage might increase patients' risk of contracting HIV, according to a team of scientists led by Susan Buchbinder, a University of California San Francisco professor and head of HIV Prevention Research at the San Francisco Department of Public Health. One of the vaccines is on the verge of phase 3 studies in Russia and Pakistan. 

Buchbinder and her colleagues have firsthand experience of this particular vaccine side effect from their previous research into a HIV vaccine. Their most promising candidate vaccine had the exact opposite effect to the desired outcome, leaving people even more vulnerable to the disease than they had been before.

“We are concerned that use of an Ad5 vector for immunisation against SARS-CoV-2 could similarly increase the risk of HIV-1 acquisition among men who receive the vaccine,” they wrote.

A vector is the method by which a vaccine is delivered to a target location. One of the more common vectors used in medical research is a genetically-modified adenovirus, a group of DNA viruses which usually cause eye and respiratory diseases. 

Several of the current batch of Covid-19 vaccines in development use an adenovirus as the delivery method for the genetic code of the coronavirus spike proteins, with a view to training our immune systems to recognize and fight off SARS-CoV-2. 

More often than not, genetically-modified adenoviruses used as vectors do not increase the risk of HIV. 

However, one specific one, called Ad5 (recombinant adenovirus type-5), was the culprit which undid Buchbinder and her team’s previous HIV vaccine and is at the center of the current vaccine controversy. 

The mechanism by which it increases the risk of contracting HIV is poorly-understood but seems to provoke the immune system in such a way that it provides HIV with even more targets than before, allowing it to gain a foothold in the body much faster. 

Immunologist Anthony Fauci, who has been director of the National Institute of Allergy and Infectious Diseases since 1984, warned against using this particular vector in vaccines distributed in areas at-risk of HIV spread back in 2014. 

Despite this, the companies behind the vaccines in question claim they are aware of the problem and have taken the risks into account during the vaccines' development. 

For example, ImmunityBio, which is currently testing its vaccine in California before the next stage which will take place in South Africa, claimed they had genetically 'muted' the Ad5 vector in their vaccine. 

Several vaccine trials have already been paused for adverse side effects and even death in one case.

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