The United States is ready to roll out Covid-19 vaccine booster shots next week but only if health regulators approve the plan, White House officials have said.

“We've been working through the last few weeks, intensely with our partners, our governors, state, and local health officials, federal pharmacy programmes, the community health centres to ensure that we are ready for next week,” White House coronavirus response coordinator Jeff Zients said at a briefing, according to Reuters.

Surgeon General Vivek Murthy told reporters boosters will be available once the FDA and the Centres for Disease Control and Prevention approve the plan.

“We have always said that this initial plan would be contingent on the FDA and the CDC's independent evaluation. We will follow that evaluation and their recommendations. We will make sure our final plan reflects it,” he said.

India will extend until the end of the year a reduction on taxes on drugs used for the treatment of Covid-19 infection, Finance Minister Nirmala Sitharaman said has said.

In June, India had cut taxes on medical equipment such as oxygen concentrators and drugs used to treat Covid-19 such as Zolgensma and Viltepso, to five per cent from 12-18pc. The cut was due to expire this month, according to a Reuters report.

Sindh has reported 665 new Covid-19 cases in the last 24 hours, according to a handout from the Chief Minister's Office, taking the province's tally of infections to 448,695.

Meanwhile, 19 more people succumbed to the virus, raising the death toll to 7,243.

According to the handout, 17,670 Covid tests were conducted in the last 24 hours while the positivity rate was recorded at 3.8 per cent.

The Gilgit-Baltistan government has failed to achieve its target of vaccinating the entire population against Covid-19 by September, it emerged on Friday.

Contrary to the target set earlier, the government has only managed to administer the vaccines to 56pc of the population so far.

The official data reveals that Hunza is the only district with 100pc vaccination rate, while Ghizer district has 80pc inoculation completed. However, in the Diamer district, only 23pc of the population has been vaccinated against Covid-19 so far.

According to the health department, 459,657 out of 815,211 people aged above 17 have been vaccinated in the region.

The head of the world's largest vaccine maker has said it is “unethical” to give third doses of the Covid-19 vaccine while developing nations are struggling to access first and second jabs.

“It's unethical to start giving three doses to somebody when others in certain countries and populations have not even got two doses,” Adar Poonawalla, billionaire chief executive of Serum Institute of India, told reporters.

He added it was “not right” to roll out booster shots when poorer countries have “not been able to get the vaccines purely because the rich nations have taken away most of the vaccines”.

A third shot of Sinopharm's Covid-19 vaccine leads to a rebound in antibody levels that drop months after a second dose, a small-scale Chinese study showed.

It also showed the booster enhanced cell-based responses to the coronavirus.

About five months after a second Sinopharm dose, the average concentration of neutralising antibody against the virus dropped by 70 per cent from the level seen four weeks after that shot, according to analysis of samples taken from vaccinated healthcare workers.

But one week after a third shot, the antibody concentration had increased 7.2-fold compared with the level seen five months after the second shot, researchers from a hospital affiliated with the Sun Yat-sen University said in the paper.

Cambodia has begun inoculating children as young as six against coronavirus, even though the World Health Organisation has yet to approve a vaccine for the under-12s.

The southeast Asian country has won praise for its swift vaccination programme, which has seen more than 98 per cent of the adult population receive at least one dose, according to the health ministry.

The latest phase of the drive began with the grandchildren of Prime Minister Hun Sen and other officials receiving a Sinovac shot in front of reporters in Phnom Penh, AFP reported.

“It is necessary for us to do this because we have to step ahead,” Hun Sen said.

Singapore Prime Minister Lee Hsien Loong has said he had received a Covid-19 vaccine booster shot and urged other elderly people to come forward to get a shot amid a new wave of infections across the city-state, Reuters reports.

"Cases are increasing rapidly. A booster jab will strengthen your protection against Covid-19," Lee, 69, said in a post on his Facebook page.

The Southeast Asia country has started giving boosters to the elderly and immunocompromised groups this week.