That didn't take long. Only a few days after Eli Lilly's COVID-19 antibody combo of bamlanivimab and etesevimab made its return to more than 20 states, federal officials are resuming distribution nationwide.

In a Thursday alert, officials said Lilly's drug "can be used in all U.S. states, territories, and jurisdictions" based on data about variants circulating nationwide. Since Eli Lilly's combo is expected to be effective against the delta variant—and because that variant is now dominant in the United States—officials are ready to again endorse the drugs.

Previously, the feds halted Lilly's antibody combo on concerns that it wouldn't work against variants first identified in Brazil and South Africa. That dealt a huge blow to Lilly's COVID-19 antibody program, which pulled in more than $800 million in the last quarter of 2020 and the first quarter of 2021. After the government's halt, sales for Lilly's COVID-19 antibodies crashed to $149 million in the second quarter of this year.

Now, studies show the meds can work against the troublesome delta variant, which has fueled a new wave of infections, hospitalizations and deaths. Meanwhile, the variants that can evade Lilly's drugs are decreasing in prevalence, the feds say, making it a good time to allow the drugs to be used.

Earlier this week, officials had authorized the drugs in more than 20 states based on data about circulating variants.

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Meanwhile, Lilly's monthslong halt created an opening for Regeneron, which has gained serious momentum in recent months with its rival Regen-Cov. That combo—comprising casirivimab and imdevimab—this summer scored another FDA authorization as a post-exposure prevention tool. 

With its dominant position on the market, Regeneron's combo pulled in $2.6 billion in the second quarter. Since then, the drug has been in high demand in states like Texas and Florida, which have been battling a summer surge of virus.

RELATED: Lilly's COVID antibody combo halted nationwide, dealing huge blow to blockbuster program

Aside from Lilly and Regeneron, GlaxoSmithKline and Vir Biotechnology have also won an FDA authorization for their monoclonal antibody sotrovimab. Those companies don't have a supply deal with the U.S., but have seen orders spike in recent weeks, a GSK spokesman said in August.

Elsewhere on the therapeutics front, Pfizer and Merck recently started late-stage studies for their oral drugs, which would mark another important weapon in the fight against the virus.