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The development of prophylactic vaccines at unprecedented speed is necessary to control the global pandemic due to SARS CoV 2 infection. Vaccines approved for use and those under development intend to block viral sites binding to the hosts cellular receptors by means of neutralizing antibodies. Virus infection is mediated by the spike glycoprotein trimer on the virion surface via its receptor binding domain (RBD). Antibody response against this domain is an important outcome of the immunization and correlates well with viral neutralization. Here we show that macromolecular constructs with recombinant RBD conjugated to tetanus toxoid induce a potent immune response in laboratory animals. Some advantages of the immunization with the viral antigen coupled to tetanus toxoid have become evident such as predominantly IgG immune response due to affinity maturation and long term specific B memory cells. This work demonstrates that subunit conjugate vaccines can be an alternative for COVID19 paving the way for other viral conjugate vaccines based on the use of small viral proteins involved in the infection process.

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