Finally, a single-dose Covid vaccine is within sight

Finally, a single-dose Covid vaccine is within sight

While all the coronavirus vaccines launched so far need two doses, Johnson & Johnson designed theirs to work with a single shot. Early data shows it is effective, and it could be approved for use by March

Abhilash.Gaur@timesgroup.com

All Covid vaccines so far work best with two doses, but the UK, which is battling an explosion of cases, last month decided to delay the second dose and give everyone their “first dose first.” The aim was to ensure some immunity in all, rather than full immunity in some.

Experts abroad were aghast. “I would not be in favour of that,” declared Dr Anthony S Fauci, a trusted voice in America. Some said the UK was straying from science and resorting to “Wild West” measures, dishonesty and short-termism.

But it now looks like America will follow the UK’s first-dose-first approach. President-elect Joe Biden “supports releasing available doses immediately, and believes the government should stop holding back vaccine supply (for second dose) so we can get more shots in Americans’ arms now,” says a CNN report.

There are valid concerns about first-dose-first. For example, a single dose might not produce sufficient immunity in the elderly, who need it the most. Also, the virus could mutate inside people who have not been fully immunised.

It’s a compromise either way, but as Tim Harford writes in the Financial Times, the question is whether giving one dose is like a bicycle with one wheel (useless) or a car with one headlight (not ideal but workable). “If forced to drive in the dark, I would rather that every car on the road had one headlight than some two and some none.”

What if such a compromise were not needed at all, if vaccines worked well enough with one dose? It would make everyone’s life easy. Fewer vials and syringes and warehouses. Fewer deliveries. And no repeat visits to clinics.

Pharma giant Johnson & Johnson took the single-dose road, and new data from human trials suggests its vaccine, called Ad26.COV2.S for now, is good.

Plenty Of Antibodies

A report in Time says the J&J vaccine produces a “long-lasting” immune response. “More than 90% of participants made... neutralising antibodies within 29 days.” By the 57th day, everyone had antibodies, and the immune response did not wane throughout the 71-day trial period.

The single-dose J&J vaccine makes more antibodies than single doses of the current crop of vaccines, as it should. A report in Stat says, after a single dose of Pfizer and Moderna’s mRNA vaccines, “only 60% of participants appeared to have neutralising antibody levels.”

How does J&J’s single dose compare with two doses of other vaccines? The company’s chief scientific officer, Paul Stoffels, told Time the response is “in the same range.” He said they had aimed for 60% overall effectiveness, and hoped and planned for 70%. He now thinks the results could be even better. Moncef Slaoui, the top scientist on America’s ‘Operation Warp Speed’ vaccine development project, agrees. He has said he “anticipates J&J’s oneshot vaccine will show 80% to 85% effectiveness against Covid-19.”

Final results of the vaccine’s trial on 45,000 volunteers are expected in two-weeks, and if it exceeds 80% efficacy, it will have emergency use authorisation in the US by March, Reuters says quoting Slaoui.

Second Dose

While the other vaccines focused only on a two-dose course, J&J is running a separate large trial with two doses. Unlike other vaccines, which are given 21-28 days apart, J&J’s booster dose is given after 57 days, so the pressure on supplies is less.

Stat says the booster dose makes the vaccine even more effective: “It doubled or tripled their levels of neutralising antibodies.” But if a single dose works well enough, the second dose might be unnecessary for most healthy people.

The vaccine has been tested in two age groups: 18-55 years, and 65-plus, and in both, Time says, “There was no difference in the immune response.” Common side effects included fever, fatigue, headache, muscle pain and injection-site pain.