Vaccine advisers to the World Health Organization said it’s OK to delay the second dose of Moderna’s coronavirus vaccine for as long as six weeks, but recommended against halving doses to try to stretch supply.
The recommendations from WHO’s Strategic Advisory Group of Experts on Immunization, or SAGE, closely mirror those made for Pfizer’s vaccine, which uses very similar technology, and recommendations from the US Centers for Disease Control and Prevention and the US Food and Drug Administration.
They focus heavily on the scarcity of vaccine and explain the logic behind the recommendations.
“Some countries have therefore considered delaying the administration of the second dose to allow for a higher initial coverage. This is based on the observation that efficacy has been shown to be 91.9%, starting 14 days after the first dose, with a median follow-up time of 28 days,” WHO said.
“There appears to be protection against COVID-19 disease following one dose; however, there is insufficient information about longer-term protection beyond 28 days after a single dose, as most trial participants received two doses. It is of note that neutralizing antibody responses were modest after the first dose and increased substantially after the second dose,” it added. “WHO’s recommendation at present is that, if judged necessary, the interval between doses may be extended to 42 days. The evidence base for this extension is not strong, but this was the longest interval for any participants in the primary efficacy analyses of the phase 3 trial, though the great majority received the second dose after a shorter interval.”
WHO also recommended focusing on vaccinating health workers at high risk of infection and older people. “Protecting high-risk health workers has a threefold purpose: (i) to protect the individual health workers; (ii) to protect critical essential services during the COVID-19 pandemic, and (iii) to prevent onward transmission to vulnerable people. Protecting older people will have the greatest public health impact in terms of reducing the number of deaths,” WHO explained.
There’s no data about what happens if people get one dose of one vaccine and then a second dose with a different vaccine. “If different COVID-19 vaccine products are inadvertently administered in the two doses, no additional doses of either vaccine are recommended at this time,” WHO said.
WHO also noticed very rare cases of a severe allergic reaction known as anaphylaxis but, like the CDC, says people with known allergies should not avoid the vaccine – unless the allergy is to polyethylene glycol (PEG), a component of the vaccine.
“The vial stoppers are not made with natural rubber latex, and there is no contraindication or precaution to vaccination for persons with a latex allergy. In addition, as mRNA-1273 does not contain eggs or gelatine, there is no contraindication or precaution to vaccination for persons with allergies to any food substances,” it says.
“Currently there are no data on the safety or efficacy of vaccination in persons who received monoclonal antibodies or convalescent plasma as part of COVID-19 treatment. Hence, as a precautionary measure, vaccination should be deferred for at least 90 days to avoid interference of the antibody treatment with vaccine-induced immune responses,” WHO concluded.