Two people died after receiving Moderna COVID-19 vaccine shots that were among lots later suspended following the discovery of contaminants, Japan's health ministry said on Saturday.
The men in their 30s died this month within days of receiving their second Moderna doses, the ministry said in a release. Each had a shot from one of three manufacturing lots suspended on Thursday. The cause of the deaths is still being investigated.
Japan halted the use of 1.63 million Moderna doses shipped to 863 vaccination centres nationwide, more than a week after the domestic distributor, Takeda Pharmaceutical, received reports of contaminants in some vials.
The government and Moderna had said no safety or efficacy issues had been identified and the suspension was just a precaution.
The contaminant is believed to be metallic particles, Japanese public broadcaster NHK reported, citing health ministry sources.
Frequently Asked Questions
A vaccine works by mimicking a natural infection. A vaccine not only induces immune response to protect people from any future COVID-19 infection, but also helps quickly build herd immunity to put an end to the pandemic. Herd immunity occurs when a sufficient percentage of a population becomes immune to a disease, making the spread of disease from person to person unlikely. The good news is that SARS-CoV-2 virus has been fairly stable, which increases the viability of a vaccine.
There are broadly four types of vaccine — one, a vaccine based on the whole virus (this could be either inactivated, or an attenuated [weakened] virus vaccine); two, a non-replicating viral vector vaccine that uses a benign virus as vector that carries the antigen of SARS-CoV; three, nucleic-acid vaccines that have genetic material like DNA and RNA of antigens like spike protein given to a person, helping human cells decode genetic material and produce the vaccine; and four, protein subunit vaccine wherein the recombinant proteins of SARS-COV-2 along with an adjuvant (booster) is given as a vaccine.
Vaccine development is a long, complex process. Unlike drugs that are given to people with a diseased, vaccines are given to healthy people and also vulnerable sections such as children, pregnant women and the elderly. So rigorous tests are compulsory. History says that the fastest time it took to develop a vaccine is five years, but it usually takes double or sometimes triple that time.