“Until our study, what hasn’t been clear is if you get exposed to one coronavirus, could you have cross-protection across other coronaviruses? And we showed that is the case,” said lead author Pablo Penaloza-MacMaster, Assistant Professor of Microbiology-Immunology at North-western University’s Feinberg School of Medicine.

Penaloza-MacMaster collaborated with North-western Medicine physician, Igor Koralnik and Lavanya Visvabharathy, a post-doctoral research associate at Feinberg, to evaluate immune responses in humans who received Covid vaccines as well as in Covid patients.

“We found that these individuals developed antibody responses that neutralised a common cold coronavirus, HCoV-OC43,” Penaloza-MacMaster said.

“We are now measuring how long this cross-protection lasts.”

The three main families of coronaviruses that cause human disease are Sarbecovirus, which includes the SARS-CoV-1 strain that was responsible for the 2003 outbreak of Severe Acute Respiratory Syndrome (SARS).

Other coronaviruses are SARS-CoV-2, which is responsible for Covid-19 pandemic; Embecovirus (that includes OC43) which is often responsible for the common cold; and Merbecovirus, which is the virus responsible for Middle East Respiratory Syndrome (MERS), first reported in 2012.

During the study published in the Journal of Clinical Investigation, plasma from humans who had been vaccinated against SARS-CoV-2 produced antibodies that were cross-reactive (provided protection) against SARS-CoV-1 and the common cold coronavirus (OC43).

The study found mice immunised with a SARS-CoV-1 vaccine developed in 2004 generated immune responses that protected them from intranasal exposure by SARS-CoV-2.

The team found prior coronavirus infections can protect against subsequent infections with other coronaviruses.

Mice that had been immunised with Covid-19 vaccines and later were exposed to the common cold coronavirus were partially protected against the common cold but the protection was much less robust, the study found.

The reason, the scientists explained, is because both SARS-CoV-1 and SARS-CoV-2 are genetically similar while the common cold coronavirus is more divergent from SARS-CoV-2.

“As long as the coronavirus is greater than 70 per cent related, the mice were protected,” Penaloza-MacMaster said.

“If they were exposed to a very different family of coronaviruses, the vaccines might confer less protection.”

Given how different each coronavirus family is, that answer is “likely no”, said the study authors. However, there may be a path forward for developing a vaccine for each coronavirus family (Sarbecovirus, Embecovirus and Merbecovirus), they said.